Cancer

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#REDIRECT [[Cancer]]

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{{Infobox disease

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| Name = Cancer

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| Image = Tumor_Mesothelioma2_legend.jpg

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| Caption = A coronal [[CT scan]] showing a malignant [[mesothelioma]]<br />Legend: → [[tumor]] ←, ✱ central [[pleural effusion]], 1 & 3 [[lungs]], 2 [[Vertebral column|spine]], 4 [[ribs]], 5 [[aorta]], 6 [[spleen]], 7 & 8 [[kidneys]], 9 [[liver]].

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| DiseasesDB = 28843

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| ICD10 ={{ICD10|C|00}}—{{ICD10|C|97}}

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| ICD9 = {{ICD9|140}}—{{ICD9|239}}

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| ICDO =

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| MedlinePlus = 001289

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| eMedicineSubj =

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| eMedicineTopic =

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| MeshID = D009369

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}}

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'''Cancer''' {{IPAc-en|audio=en-us-cancer.ogg|ˈ|k|æ|n|s|ər}}, known medically as a [[malignancy|malignant]] [[neoplasm]], is a broad group of various [[disease]]s, all involving unregulated cell growth. In cancer, [[cell (biology)|cells]] divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also [[metastasis|spread]] to more distant parts of the body through the [[lymph|lymphatic system]] or [[blood]]stream. Not all tumors are cancerous. [[Benign tumor]]s do not grow uncontrollably, do not invade neighboring tissues, and do not spread throughout the body. There are over 200 different known cancers that afflict humans.<ref>{{cite web |url=http://cancerhelp.cancerresearchuk.org/about-cancer/cancer-questions/how-many-different-types-of-cancer-are-there |title=How many different types of cancer are there? : Cancer Research UK : CancerHelp UK |format= |work= |accessdate=11 May 2012}}</ref>

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Determining what causes cancer is complex. Many things are known to increase the risk of cancer, including [[tobacco]] use, certain [[infection]]s, [[radiation]], [[lack of physical activity]], [[obesity]], and environmental pollutants.<ref name=Enviro2008>{{cite journal | author = Anand P, Kunnumakkara AB, Kunnumakara AB, Sundaram C, Harikumar KB, Tharakan ST, Lai OS, Sung B, Aggarwal BB | title = Cancer is a preventable disease that requires major lifestyle changes | journal = Pharm. Res. | volume = 25 | issue = 9 | pages = 2097–116 | year = 2008 | month = September | pmid = 18626751 | pmc = 2515569 | doi = 10.1007/s11095-008-9661-9 }}</ref> These can directly damage genes or combine with existing genetic faults within cells to cause the disease.<ref name="Kinz">{{cite book | author = Kinzler, Kenneth W.; Vogelstein, Bert | title = The genetic basis of human cancer | edition = 2nd, illustrated, revised| publisher = McGraw-Hill, Medical Pub. Division | location = New York | year = 2002 | page = 5| isbn = 978-0-07-137050-9 | url = http://books.google.com/?id=pYG09OPbXp0C| chapter=Introduction |chapterurl=http://books.google.co.uk/books?id=pYG09OPbXp0C&pg=PA5}}</ref> Approximately five to ten percent of cancers are entirely hereditary.

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Cancer can be detected in a number of ways, including the presence of certain [[cancer symptoms|signs and symptoms]], [[cancer screening|screening tests]], or [[medical imaging]]. Once a possible cancer is detected it is diagnosed by [[histology|microscopic examination]] of a [[biopsy|tissue sample]]. Cancer is usually treated with [[chemotherapy]], [[radiation therapy]] and [[surgery]]. The chances of surviving the disease vary greatly by the type and location of the cancer and the extent of disease at the start of treatment. While cancer can affect people of all ages, and a few types of cancer are more common in children, the risk of developing cancer generally increases with age. In 2007, cancer caused about 13% of [[causes of death|all human deaths]] worldwide (7.9 million). Rates are rising as more people live to an old age and as mass lifestyle changes occur in the developing world.<ref name=Epi11/>

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==Signs and symptoms==

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[[Image:Symptoms of cancer metastasis.svg|thumb|Symptoms of [[cancer metastasis]] depend on the location of the tumor.]]

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When cancer begins it invariably produces no symptoms with signs and symptoms only appearing as the mass continues to grow or [[ulcer (dermatology)|ulcerates]]. The findings that result depends on the type and location of the cancer. Few symptoms are [[non-specific symptom|specific]], with many of them also frequently occurring in individuals who have other conditions. Cancer is the new "[[the great imitator|great imitator]]". Thus it is not uncommon for people diagnosed with cancer to have been treated for other diseases to which it was assumed their symptoms were due.<ref name=Card10>Holland Chp. 1</ref>

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===Local effects===

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Local symptoms may occur due to the mass of the tumor or its ulceration. For example, mass effects from [[lung cancer]] can cause blockage of the [[bronchus]] resulting in [[cough]] or [[pneumonia]]; [[esophageal cancer]] can cause narrowing of the esophagus, making it difficult or painful to swallow; and [[colorectal cancer]] may lead to narrowing or blockages in the bowel, resulting in changes in bowel habits. Masses of breast or testicles may be easily felt. [[ulcer (dermatology)|Ulceration]] can cause bleeding which, if it occurs in the lung, will lead to [[hemoptysis|coughing up blood]], in the bowels to [[anemia]] or [[Lower gastrointestinal bleeding|rectal bleeding]], in the bladder to blood in the urine, and in the uterus to vaginal bleeding. Although localized pain may occur in advanced cancer, the initial swelling is usually painless. Some cancers can cause build up of fluid within the chest or abdomen.<ref name=Card10/>

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===Systemic symptoms===

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General symptoms occur due to distant effects of the cancer that are not related to direct or metastatic spread. These may include: unintentional weight loss, [[fever]], being excessively tired, and changes to the skin.<ref>{{cite book|last=O'Dell|first=edited by Michael D. Stubblefield, Michael W.|title=Cancer rehabilitation principles and practice|year=2009|publisher=Demos Medical|location=New York|isbn=978-1-933864-33-4|page=983|url=http://books.google.ca/books?id=_JaPlNYgXkEC&pg=PT983}}</ref> [[Hodgkin disease]], [[leukemia]]s, and cancers of the liver or kidney can cause a persistent [[fever of unknown origin]].<ref name=Card10/>

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Specific constellations of systemic symptoms, termed [[paraneoplastic phenomenon|paraneoplastic phenomena]], may occur with some cancers. Examples include the appearance of [[myasthenia gravis]] in [[thymoma]] and [[nail clubbing|clubbing]] in [[lung cancer]].<ref name=Card10/>

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===Metastasis===

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[[Symptoms of metastasis]] are due to the spread of cancer to other locations in the body. They can include enlarged [[lymph node]]s (which can be felt or sometimes seen under the skin and are typically hard), [[hepatomegaly]] (enlarged liver) or [[splenomegaly]] (enlarged spleen) which can be felt in the [[abdomen]], pain or [[fracture]] of affected bones, and [[neurology|neurological]] symptoms.<ref name=Card10/>

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==Causes==

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Cancers are primarily an environmental disease with 90–95% of cases attributed to environmental factors and 5–10% due to genetics.<ref name=Enviro2008/> [[Environment (biophysical)|''Environmental'']], as used by cancer researchers, means any cause that is not [[Heredity|inherited genetically]], not merely pollution.<ref name="isbn0-387-78192-7">{{cite book | author = Kravchenko J, Akushevich I, Manton, KG | title = Cancer mortality and morbidity patterns in the U. S. population: an interdisciplinary approach | publisher = Springer | location = Berlin | year = 2009 | pages = | isbn = 0-387-78192-7 | quote = The term ''environment'' refers not only to air, water, and soil but also to substances and conditions at home and at the workplace, including diet, smoking, alcohol, drugs, exposure to chemicals, sunlight, ionizing radiation, electromagnetic fields, infectious agents, etc. Lifestyle, economic and behavioral factors are all aspects of our environment. }}</ref> Common environmental factors that contribute to cancer death include [[tobacco]] (25–30%), diet and [[obesity]] (30–35%), [[infections]] (15–20%), [[radiation]] (both ionizing and non-ionizing, up to 10%), stress, lack of [[physical activity]], and [[environmental pollutants]].<ref name=Enviro2008/>

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It is nearly impossible to prove what caused a cancer in any individual, because most cancers have multiple possible causes. For example, if a person who uses tobacco heavily develops lung cancer, then it was probably caused by the tobacco use, but since everyone has a small chance of developing lung cancer as a result of air pollution or radiation, then there is a small chance that the cancer developed because of air pollution or radiation.

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===Chemicals===

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[[Image:Cancer smoking lung cancer correlation from NIH.svg|thumb|right|The incidence of [[lung cancer]] is highly correlated with [[smoking]].]]

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Cancer pathogenesis is traceable back to [[DNA mutations]] that impact cell growth and metastasis. Substances that cause DNA mutations are known as mutagens, and mutagens that cause cancers are known as carcinogens. Particular substances have been linked to specific types of cancer. [[Tobacco smoking]] is associated with many forms of cancer,<ref name=Sasco>{{cite journal | author = Sasco AJ, Secretan MB, Straif K | title = Tobacco smoking and cancer: a brief review of recent epidemiological evidence | journal = Lung Cancer | volume = 45 Suppl 2 | issue = | pages = S3–9 | year = 2004 | month = August | pmid = 15552776 | doi = 10.1016/j.lungcan.2004.07.998 }}</ref> and causes 90% of [[lung cancer]].<ref name="pmid9594919">{{cite journal | author = Biesalski HK, Bueno de Mesquita B, Chesson A, Chytil F, Grimble R, Hermus RJ, Köhrle J, Lotan R, Norpoth K, Pastorino U, Thurnham D | title = European Consensus Statement on Lung Cancer: risk factors and prevention. Lung Cancer Panel | journal = CA Cancer J Clin | volume = 48 | issue = 3 | pages = 167–76; discussion 164–6 | year = 1998 | pmid = 9594919 | doi = 10.3322/canjclin.48.3.167 }}</ref>

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Many [[mutagen]]s are also [[carcinogen]]s, but some carcinogens are not mutagens. [[Alcohol]] is an example of a chemical carcinogen that is not a mutagen.<ref name="pmid9751943">{{cite journal | author = Seitz HK, Pöschl G, Simanowski UA | title = Alcohol and cancer | journal = Recent Dev Alcohol | volume = 14 | issue = | pages = 67–95 | year = 1998 | pmid = 9751943 | doi = }}</ref> In Western Europe 10% of cancers in males and 3% of cancers in females are attributed to alcohol.<ref name="pmid21474525">{{cite journal | author = Schütze M, Boeing H, Pischon T, Rehm J, Kehoe T, Gmel G, Olsen A, Tjønneland AM, Dahm CC, Overvad K, Clavel-Chapelon F, Boutron-Ruault MC, Trichopoulou A, Benetou V, Zylis D, Kaaks R, Rohrmann S, Palli D, Berrino F, Tumino R, Vineis P, Rodríguez L, Agudo A, Sánchez MJ, Dorronsoro M, Chirlaque MD, Barricarte A, Peeters PH, van Gils CH, Khaw KT, Wareham N, Allen NE, Key TJ, Boffetta P, Slimani N, Jenab M, Romaguera D, Wark PA, Riboli E, Bergmann MM | title = Alcohol attributable burden of incidence of cancer in eight European countries based on results from prospective cohort study | journal = BMJ | volume = 342 | issue = | pages = d1584 | year = 2011 | pmid = 21474525 | pmc = 3072472 | doi = 10.1136/bmj.d1584 }}</ref>

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Decades of research has demonstrated the link between [[tobacco]] use and cancer in the [[lung cancer|lung]], [[larynx]], head, neck, stomach, bladder, kidney, [[esophagus]] and [[pancreas]].<ref name="pmid12270001">{{cite journal | author = Kuper H, Boffetta P, Adami HO | title = Tobacco use and cancer causation: association by tumour type | journal = J. Intern. Med. | volume = 252 | issue = 3 | pages = 206–24 | year = 2002 | month = September | pmid = 12270001 | doi = 10.1046/j.1365-2796.2002.01022.x }}</ref> Tobacco smoke contains over fifty known carcinogens, including [[nitrosamine]]s and [[polycyclic aromatic hydrocarbon]]s.<ref name=Kuper/> Tobacco is responsible for about one in three of all cancer deaths in the developed world,<ref name=Sasco/> and about one in five worldwide.<ref name=Kuper>{{cite journal | author = Kuper H, Adami HO, Boffetta P | title = Tobacco use, cancer causation and public health impact | journal = J. Intern. Med. | volume = 251 | issue = 6 | pages = 455–66 | year = 2002 | month = June | pmid = 12028500 | doi = 10.1046/j.1365-2796.2002.00993.x }}</ref> [[Lung cancer]] death rates in the United States have mirrored [[tobacco smoking|smoking]] patterns, with increases in smoking followed by dramatic increases in lung cancer death rates and, more recently, decreases in smoking rates since the 1950s followed by decreases in lung cancer death rates in men since 1990.<ref name="pmid16998161">{{cite journal | author = Thun MJ, Jemal A | title = How much of the decrease in cancer death rates in the United States is attributable to reductions in tobacco smoking? | journal = Tob Control | volume = 15 | issue = 5 | pages = 345–7 | year = 2006 | month = October | pmid = 16998161 | pmc = 2563648 | doi = 10.1136/tc.2006.017749 }}</ref><ref name="pmid18434333">{{cite journal | author = Dubey S, Powell CA | title = Update in lung cancer 2007 | journal = Am. J. Respir. Crit. Care Med. | volume = 177 | issue = 9 | pages = 941–6 | year = 2008 | month = May | pmid = 18434333 | pmc = 2720127 | doi = 10.1164/rccm.200801-107UP }}</ref> However, the numbers of smokers worldwide is still rising, leading to what some organizations have described as the ''tobacco epidemic''.<ref name="pmid15217537">{{cite journal | author = Proctor RN | title = The global smoking epidemic: a history and status report | journal = Clin Lung Cancer | volume = 5 | issue = 6 | pages = 371–6 | year = 2004 | month = May | pmid = 15217537 | doi = 10.3816/CLC.2004.n.016 }}</ref>

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Cancer related to one's occupation is believed to represent between 2–20% of all cases.<ref name="pmid18055160">{{cite journal | author = Irigaray P, Newby JA, Clapp R, Hardell L, Howard V, Montagnier L, Epstein S, Belpomme D | title = Lifestyle-related factors and environmental agents causing cancer: an overview | journal = Biomed. Pharmacother. | volume = 61 | issue = 10 | pages = 640–58 | year = 2007 | month = December | pmid = 18055160 | doi = 10.1016/j.biopha.2007.10.006 }}</ref> Every year, at least 200,000 people die worldwide from cancer related to their workplace.<ref name=WHO_occup>{{cite press release |title=WHO calls for prevention of cancer through healthy workplaces |publisher=World Health Organization |date=27 April 2007 |url=http://www.who.int/mediacentre/news/notes/2007/np19/en/index.html |accessdate=13 October 2007}}</ref> Most cancer deaths caused by occupational risk factors occur in the developed world.<ref name=WHO_occup/> It is estimated that approximately 20,000 cancer deaths and 40,000 new cases of cancer each year in the U.S. are attributable to occupation.<ref>{{cite web|url=http://www.cdc.gov/niosh/topics/cancer/|title=National Institute for Occupational Safety and Health- Occupational Cancer |accessdate=13 October 2007|publisher=United States National Institute for Occupational Safety and Health}}</ref> Millions of workers run the risk of developing cancers such as [[lung cancer]] and [[mesothelioma]] from inhaling [[asbestos]] fibers and tobacco smoke, or [[leukemia]] from exposure to [[benzene]] at their workplaces.<ref name=WHO_occup/>

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===Diet and exercise===

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Diet, [[Physical activity|physical inactivity]], and [[obesity]] are related to approximately 30–35% of cancer deaths.<ref name=Enviro2008/><ref name=Nutri06/> In the United States excess body weight is associated with the development of many types of cancer and is a factor in 14–20% of all cancer deaths.<ref name=Nutri06/> Physical inactivity is believed to contribute to cancer risk not only through its effect on body weight but also through negative effects on [[immune system]] and [[endocrine system]].<ref name=Nutri06/> More than half of the effect from diet is due to [[overnutrition]] rather than from eating too few healthful foods.

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Diets that are very low in vegetables, fruits and whole grains, and high in [[processed meat|processed]] or red meats are linked with a number of cancers.<ref name=Nutri06>{{cite journal | author = Kushi LH, Byers T, Doyle C, Bandera EV, McCullough M, McTiernan A, Gansler T, Andrews KS, Thun MJ | title = American Cancer Society Guidelines on Nutrition and Physical Activity for cancer prevention: reducing the risk of cancer with healthy food choices and physical activity | journal = CA Cancer J Clin | volume = 56 | issue = 5 | pages = 254–81; quiz 313–4 | year = 2006 | pmid = 17005596 | doi = 10.3322/canjclin.56.5.254 }}</ref> A high-[[salt]] diet is linked to [[gastric cancer]], [[aflatoxin B1]], a frequent food contaminate, with liver cancer, and [[Betel nut]] chewing with oral cancer.<ref name="pmid18990005">{{cite journal | author = Park S, Bae J, Nam BH, Yoo KY | title = Aetiology of cancer in Asia | journal = Asian Pac. J. Cancer Prev. | volume = 9 | issue = 3 | pages = 371–80 | year = 2008 | pmid = 18990005 | doi = | url = http://www.apocpcontrol.org/page/popup_paper_file_view.php?pno=MzcxIFBhcmsucCZrY29kZT04MjI=&pgubun=i | format = PDF }}</ref> This may partly explain differences in cancer incidence in different countries. For example, [[gastric cancer]] is more common in Japan due to its high-salt diet<ref name="pmid19107449">{{cite journal | author = Brenner H, Rothenbacher D, Arndt V | title = Epidemiology of stomach cancer | journal = Methods Mol. Biol. | volume = 472 | issue = | pages = 467–77 | year = 2009 | pmid = 19107449 | doi = 10.1007/978-1-60327-492-0_23 }}</ref> and [[Colorectal cancer|colon cancer]] is more common in the United States. Immigrants develop the risk of their new country, often within one generation, suggesting a substantial link between diet and cancer.<ref name="pmid14278899">{{cite journal | author = Buell P, Dunn JE | title = Cancer mortality among Japanese Issei and Nisei of California | journal = Cancer | volume = 18 | issue = 5 | pages = 656–64 | year = 1965 | month = May | pmid = 14278899 | doi = 10.1002/1097-0142(196505)18:5<656::AID-CNCR2820180515>3.0.CO;2-3 }}</ref>

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===Infection===

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Worldwide approximately 18% of cancer deaths are related to [[infectious diseases]].<ref name=Enviro2008/> This proportion varies in different regions of the world from a high of 25% in Africa to less than 10% in the developed world.<ref name=Enviro2008/> [[Virus]]es are the usual infectious agents that cause cancer but [[bacteria]] and [[parasites]] may also have an effect.

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A virus that can cause cancer is called an ''[[oncovirus]]''. These include [[human papillomavirus]] ([[cervical carcinoma]]), [[Epstein-Barr virus]] ([[B-cell lymphoproliferative disease]] and [[nasopharyngeal carcinoma]]), [[Kaposi's sarcoma herpesvirus]] ([[Kaposi's Sarcoma]] and primary effusion lymphomas), [[hepatitis B]] and [[hepatitis C]] viruses ([[hepatocellular carcinoma]]), and [[Human T-cell leukemia virus-1]] (T-cell leukemias). Bacterial infection may also increase the risk of cancer, as seen in [[Helicobacter pylori]]-induced [[gastric carcinoma]].<ref name=Viral04>{{cite journal | author = Pagano JS, Blaser M, Buendia MA, Damania B, Khalili K, Raab-Traub N, Roizman B | title = Infectious agents and cancer: criteria for a causal relation | journal = Semin. Cancer Biol. | volume = 14 | issue = 6 | pages = 453–71 | year = 2004 | month = December | pmid = 15489139 | doi = 10.1016/j.semcancer.2004.06.009 }}</ref> Parasitic infections strongly associated with cancer include ''[[Schistosoma haematobium]]'' ([[Bladder cancer|squamous cell carcinoma of the bladder]]) and the [[liver fluke]]s, ''[[Opisthorchis viverrini]]'' and ''[[Clonorchis sinensis]]'' ([[cholangiocarcinoma]]).<ref name="pmid20539059">{{cite journal | author = Samaras V, Rafailidis PI, Mourtzoukou EG, Peppas G, Falagas ME | title = Chronic bacterial and parasitic infections and cancer: a review | journal = J Infect Dev Ctries | volume = 4 | issue = 5 | pages = 267–81 | year = 2010 | month = May | pmid = 20539059 | doi = | url = http://www.jidc.org/index.php/journal/article/download/20539059/387 | format = PDF }}</ref>

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===Radiation===

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Up to 10% of invasive cancers are related to radiation exposure, including both [[ionizing radiation]] and [[non-ionizing radiation|non-ionizing]] [[ultraviolet radiation]] .<ref name=Enviro2008/> Additionally, the vast majority of non-invasive cancers are non-melanoma skin cancers caused by non-ionizing [[ultraviolet radiation]].

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Sources of ionizing radiation include [[medical imaging]], and [[radon]] gas. Radiation can cause cancer in most parts of the body, in all animals, and at any age, although radiation-induced solid tumors usually take 10–15 years, and can take up to 40 years, to become clinically manifest, and radiation-induced [[leukemia]]s typically require 2–10 years to appear.<ref name=Little /> Some people, such as those with [[nevoid basal cell carcinoma syndrome]] or [[retinoblastoma]], are more susceptible than average to developing cancer from radiation exposure.<ref name=Little /> Children and adolescents are twice as likely to develop radiation-induced leukemia as adults; radiation exposure before birth has ten times the effect.<ref name=Little /> Ionizing radiation is not a particularly strong mutagen.<ref name=Little /> Residential exposure to radon gas, for example, has similar cancer risks as [[passive smoking]].<ref name=Little /> Low-dose exposures, such as living near a [[nuclear power plant]], are generally believed to have no or very little effect on cancer development.<ref name=Little /> Radiation is a more potent source of cancer when it is combined with other cancer-causing agents, such as radon gas exposure plus smoking tobacco.<ref name=Little />

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Unlike chemical or physical triggers for cancer, ionizing radiation hits molecules within cells randomly. If it happens to strike a [[chromosome]], it can break the chromosome, result in an [[aneuploidy|abnormal number of chromosomes]], inactivate one or more genes in the part of the chromosome that it hit, delete parts of the DNA sequence, cause [[chromosome translocation]]s, or cause other types of [[chromosome abnormalities]].<ref name=Little /> Major damage normally results in the cell dying, but smaller damage may leave a stable, partly functional cell that may be capable of proliferating and developing into cancer, especially if [[tumor suppressor gene]]s were damaged by the radiation.<ref name=Little>{{cite book | editor = Kufe DW, Pollock RE, Weichselbaum RR, Bast RC Jr, Gansler TS, Holland JF, Frei E III | title = Cancer medicine | author = Little JB | chapter = Chapter 14: Ionizing Radiation | edition = 6th | publisher = B.C. Decker | location = Hamilton, Ont | year = 2000 | isbn = 1-55009-113-1 | url = http://www.ncbi.nlm.nih.gov/books/NBK20793/ }}</ref> Three independent stages appear to be involved in the creation of cancer with ionizing radiation: morphological changes to the cell, acquiring [[cellular immortality]] (losing normal, life-limiting cell regulatory processes), and adaptations that favor formation of a tumor.<ref name=Little /> Even if the radiation particle does not strike the DNA directly, it triggers responses from cells that indirectly increase the likelihood of mutations.<ref name=Little />

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Medical use of ionizing radiation is a growing source of radiation-induced cancers. Ionizing radiation may be used to treat other cancers, but this may, in some cases, induce a second form of cancer.<ref name=Little /> It is also used in some kinds of [[medical imaging]]. One report estimates that approximately 29,000 future cancers could be related to the approximately 70 million [[CT scan]]s performed in the US in 2007.<ref name="pmid20008689">{{cite journal | author = Berrington de González A, Mahesh M, Kim KP, Bhargavan M, Lewis R, Mettler F, Land C | title = Projected cancer risks from computed tomographic scans performed in the United States in 2007 | journal = Arch. Intern. Med. | volume = 169 | issue = 22 | pages = 2071–7 | year = 2009 | month = December | pmid = 20008689 | doi = 10.1001/archinternmed.2009.440 }}</ref> It is estimated that 0.4% of cancers in 2007 in the United States are due to CTs performed in the past and that this may increase to as high as 1.5–2% with rates of CT usage during this same time period.<ref name="pmid18046031">{{cite journal | author = Brenner DJ, Hall EJ | title = Computed tomography—an increasing source of radiation exposure | journal = N. Engl. J. Med. | volume = 357 | issue = 22 | pages = 2277–84 | year = 2007 | month = November | pmid = 18046031 | doi = 10.1056/NEJMra072149 }}</ref>

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Prolonged exposure to [[ultraviolet radiation]] from the [[sun]] can lead to [[melanoma]] and other skin malignancies.<ref name=Cleaver>{{cite book | author = Cleaver JE, Mitchell DL | editor = Bast RC, Kufe DW, Pollock RE, ''et al.''| title = Holland-Frei Cancer Medicine | edition = 5th | publisher = B.C. Decker | location = Hamilton, Ontario | year = 2000 | chapter = 15. Ultraviolet Radiation Carcinogenesis | isbn = 1-55009-113-1 | oclc = | url = http://www.ncbi.nlm.nih.gov/books/NBK20854/ | accessdate= 31 January 2011 }}</ref> Clear evidence establishes ultraviolet radiation, especially the non-ionizing medium wave [[UVB]], as the cause of most non-melanoma [[skin cancer]]s, which are the most common forms of cancer in the world.<ref name=Cleaver />

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Non-ionizing [[radio frequency]] radiation from [[mobile phone]]s, [[electric power transmission]], and other similar sources have been described as a [[possible carcinogen]] by the [[World Health Organization]]'s [[International Agency for Research on Cancer]].<ref>{{cite web|title=IARC classifies radiofrequency electromagnetic fields as possibly carcinogenic to humans |url=http://www.iarc.fr/en/media-centre/pr/2011/pdfs/pr208_E.pdf|work=World Health Organization}}</ref>

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===Heredity===

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The vast majority of cancers are non-hereditary ("sporadic cancers"). [[Hereditary cancer]]s are primarily caused by an inherited genetic defect. Less than 0.3% of the population are carriers of a genetic mutation which has a large effect on cancer risk and these cause less than 3–10% of all cancer.<ref name=Expert09>{{cite journal | author = Roukos DH | title = Genome-wide association studies: how predictable is a person's cancer risk? | journal = Expert Rev Anticancer Ther | volume = 9 | issue = 4 | pages = 389–92 | year = 2009 | month = April | pmid = 19374592 | doi = 10.1586/era.09.12 }}</ref> Some of these [[syndrome]]s include: certain inherited mutations in the genes ''[[BRCA1]]'' and ''[[BRCA2]]'' with a more than 75% risk of [[breast cancer]] and [[ovarian cancer]],<ref name=Expert09/> and [[hereditary nonpolyposis colorectal cancer]] (HNPCC or Lynch syndrome) which is present in about 3% of people with [[colorectal cancer]],<ref name=Lancet10>{{cite journal | author = Cunningham D, Atkin W, Lenz HJ, Lynch HT, Minsky B, Nordlinger B, Starling N | title = Colorectal cancer | journal = Lancet | volume = 375 | issue = 9719 | pages = 1030–47 | year = 2010 | month = March | pmid = 20304247 | doi = 10.1016/S0140-6736(10)60353-4 }}</ref> among others.

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===Physical agents===

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Some substances cause cancer primarily through their physical, rather than chemical, effects on cells.<ref name=Maltoni>{{cite book | author = Maltoni CFM, Holland JF | editor = Bast RC, Kufe DW, Pollock RE, ''et al.'' | title = Holland-Frei Cancer Medicine | edition = 5th | publisher = B.C. Decker | location = Hamilton, Ontario | year = 2000 | chapter = Chapter 16: Physical Carcinogens | isbn = 1-55009-113-1 | url = http://www.ncbi.nlm.nih.gov/books/NBK20770/ | accessdate = 31 January 2011}}</ref>

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A prominent example of this is prolonged exposure to [[asbestos]], naturally occurring mineral fibers which are a major cause of [[mesothelioma]], a type of cancer of the [[serous membrane]].<ref name=Maltoni /> Other substances in this category, including both naturally occurring and synthetic asbestos-like fibers such as [[wollastonite]], [[attapulgite]], [[glass wool]], and [[rock wool]], are believed to have similar effects.<ref name=Maltoni />

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Nonfibrous particulate materials that cause cancer include powdered metallic [[cobalt]] and [[nickel]], and [[crystalline silica]] ([[quartz]], [[cristobalite]], and [[tridymite]]).<ref name=Maltoni />

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Usually, physical carcinogens must get inside the body (such as through inhaling tiny pieces) and require years of exposure to develop cancer.<ref name=Maltoni />

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Physical trauma resulting in cancer is relatively rare.<ref name=Gaeta>{{cite book|author=Gaeta, John F|editor=Bast RC, Kufe DW, Pollock RE, ''et al.''|title=Holland-Frei Cancer Medicine|edition=5th|publisher=B.C. Decker|location=Hamilton, Ontario|year=2000|chapter=Chapter 17: Trauma and Inflammation|isbn=1-55009-113-1|oclc=|url=http://www.ncbi.nlm.nih.gov/books/NBK20784/|accessdate=27 January 2011}}</ref> Claims that breaking bone resulted in bone cancer, for example, have never been proven.<ref name=Gaeta /> Similarly, physical trauma is not accepted as a cause for cervical cancer, breast cancer, or brain cancer.<ref name=Gaeta />

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One accepted source is frequent, long-term application of hot objects to the body. It is possible that repeated burns on the same part of the body, such as those produced by [[kanger]] and kairo heaters (charcoal [[hand warmer]]s), may produce skin cancer, especially if carcinogenic chemicals are also present.<ref name=Gaeta /> Frequently drinking scalding hot tea may produce esophageal cancer.<ref name=Gaeta />

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Generally, it is believed that the cancer arises, or a pre-existing cancer is encouraged, during the process of repairing the trauma, rather than the cancer being caused directly by the trauma.<ref name=Gaeta /> However, repeated injuries to the same tissues might promote excessive cell proliferation, which could then increase the odds of a cancerous mutation. There is no evidence that [[inflammation]] itself causes cancer.<ref name=Gaeta />

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===Hormones===

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Some [[hormone]]s play a role in the development of cancer by promoting [[cell proliferation]].<ref name=Henderson>{{cite book | author = Henderson BE, Bernstein L, Ross

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RK | editor = Bast RC, Kufe DW, Pollock RE, ''et al.''

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|title=Holland-Frei Cancer Medicine

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|edition=5th

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|publisher=B.C. Decker

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|location=Hamilton, Ontario

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|year=2000

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|chapter=Chapter 13: Hormones and the Etiology of Cancer

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|isbn=1-55009-113-1

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|oclc=

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|url=http://www.ncbi.nlm.nih.gov/books/NBK20759/

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|accessdate=27 January 2011}}</ref> Hormones are important agents in sex-related cancers such as cancer of the breast, [[endometrium]], prostate, ovary, and [[testis]], and also of [[thyroid cancer]] and [[bone cancer]].<ref name=Henderson />

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An individual's hormone levels are mostly determined genetically, so this may at least partly explains the presence of some cancers that run in families that do not seem to have any cancer-causing genes.<ref name=Henderson /> For example, the daughters of women who have breast cancer have significantly higher levels of [[estrogen]] and [[progesterone]] than the daughters of women without breast cancer. These higher hormone levels may explain why these women have higher risk of breast cancer, even in the absence of a breast-cancer gene.<ref name=Henderson /> Similarly, men of African ancestry have significantly higher levels of testosterone than men of European ancestry, and have a correspondingly much higher level of prostate cancer.<ref name=Henderson /> Men of Asian ancestry, with the lowest levels of testosterone-activating [[androstanediol glucuronide]], have the lowest levels of prostate cancer.<ref name=Henderson />

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However, non-genetic factors are also relevant: obese people have higher levels of some hormones associated with cancer and a higher rate of those cancers.<ref name=Henderson /> Women who take [[Hormone replacement therapy (menopause)|hormone replacement therapy]] have a higher risk of developing cancers associated with those hormones.<ref name=Henderson /> On the other hand, people who exercise far more than average have lower levels of these hormones, and lower risk of cancer.<ref name=Henderson /> [[Osteosarcoma]] may be promoted by [[growth hormone]]s.<ref name=Henderson /> Some treatments and prevention approaches leverage this cause by artificially reducing hormone levels, and thus discouraging hormone-sensitive cancers.<ref name=Henderson />

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===Other===

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Excepting the rare transmissions that occur with pregnancies and only a marginal few organ donors, cancer is generally not a [[transmission (medicine)|transmissible disease]]. The main reason for this is tissue graft rejection caused by [[major histocompatibility complex|MHC]] [[histocompatibility|incompatibility]].<ref name=Tolar>{{cite journal | author = Tolar J, Neglia JP | title = Transplacental and other routes of cancer transmission between individuals | journal = J. Pediatr. Hematol. Oncol. | volume = 25 | issue = 6 | pages = 430–4 | year = 2003 | month = June | pmid = 12794519 | doi = 10.1097/00043426-200306000-00002 }}</ref> In humans and other vertebrates, the immune system uses MHC antigens to differentiate between "self" and "non-self" cells because these antigens are different from person to person. When non-self antigens are encountered, the immune system reacts against the appropriate cell. Such reactions may protect against tumour cell engraftment by eliminating implanted cells. In the United States, approximately 3,500 pregnant women have a malignancy annually, and transplacental transmission of [[acute leukaemia]], [[lymphoma]], [[melanoma]] and [[carcinoma]] from mother to fetus has been observed.<ref name=Tolar/> The development of donor-derived tumors from organ transplants is exceedingly rare. The main cause of organ transplant associated tumors seems to be malignant melanoma, that was undetected at the time of organ harvest.<ref name="pmid16957717">{{cite journal | author = Dingli D, Nowak MA | title = Cancer biology: infectious tumour cells | journal = Nature | volume = 443 | issue = 7107 | pages = 35–6 | year = 2006 | month = September | pmid = 16957717 | pmc = 2711443 | doi = 10.1038/443035a | bibcode = 2006Natur.443...35D }}</ref> Job stress does not appear to be a significant factor at least in lung, colorectal, breast and prostate cancers.<ref>{{cite journal|last=Heikkilä|first=K|coauthors=Nyberg, ST; Theorell, T; Fransson, EI; Alfredsson, L; Bjorner, JB; Bonenfant, S; Borritz, M; Bouillon, K; Burr, H; Dragano, N; Geuskens, GA; Goldberg, M; Hamer, M; Hooftman, WE; Houtman, IL; Joensuu, M; Knutsson, A; Koskenvuo, M; Koskinen, A; Kouvonen, A; Madsen, IE; Magnusson Hanson, LL; Marmot, MG; Nielsen, ML; Nordin, M; Oksanen, T; Pentti, J; Salo, P; Rugulies, R; Steptoe, A; Suominen, S; Vahtera, J; Virtanen, M; Väänänen, A; Westerholm, P; Westerlund, H; Zins, M; Ferrie, JE; Singh-Manoux, A; Batty, GD; Kivimäki, M; IPD-Work, Consortium|title=Work stress and risk of cancer: meta-analysis of 5700 incident cancer events in 116 000 European men and women.|journal=BMJ (Clinical research ed.)|date=2013 Feb 7|volume=346|pages=f165|pmid=23393080}}</ref>

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==Pathophysiology==

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[[File:Cancer requires multiple mutations from NIHen.png|thumb|right|Cancers are caused by a series of mutations. Each mutation alters the behavior of the cell somewhat.]]

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Cancer is fundamentally a disease of failure of regulation of tissue growth. In order for a normal cell to [[malignant transformation|transform]] into a cancer cell, the [[genes]] which regulate cell growth and differentiation must be altered.<ref name="pmid18234754">{{cite journal | author = Croce CM | title = Oncogenes and cancer | journal = N. Engl. J. Med. | volume = 358 | issue = 5 | pages = 502–11 | year = 2008 | month = January | pmid = 18234754 | doi = 10.1056/NEJMra072367 }}</ref>

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The affected genes are divided into two broad categories. [[Oncogene]]s are genes which promote cell growth and reproduction. [[Tumor suppressor gene]]s are genes which inhibit cell division and survival. Malignant transformation can occur through the formation of novel oncogenes, the inappropriate over-expression of normal oncogenes, or by the under-expression or disabling of tumor suppressor genes. Typically, changes in ''many'' genes are required to transform a normal cell into a cancer cell.<ref name="pmid11905807">{{cite journal | author = Knudson AG | title = Two genetic hits (more or less) to cancer | journal = Nat. Rev. Cancer | volume = 1 | issue = 2 | pages = 157–62 | year = 2001 | month = November | pmid = 11905807 | doi = 10.1038/35101031 }}</ref>

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Genetic changes can occur at different levels and by different mechanisms. The gain or loss of an entire [[chromosome]] can occur through errors in [[mitosis]]. More common are [[mutation]]s, which are changes in the [[nucleotide]] sequence of genomic DNA.

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Large-scale mutations involve the deletion or gain of a portion of a chromosome. [[Gene duplication|Genomic amplification]] occurs when a cell gains many copies (often 20 or more) of a small chromosomal locus, usually containing one or more oncogenes and adjacent genetic material. [[Chromosomal translocation|Translocation]] occurs when two separate chromosomal regions become abnormally fused, often at a characteristic location. A well-known example of this is the [[Philadelphia chromosome]], or translocation of chromosomes 9 and 22, which occurs in [[chronic myelogenous leukemia]], and results in production of the [[BCR gene|BCR]]-[[abl gene|abl]] [[fusion protein]], an oncogenic [[tyrosine kinase]].

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Small-scale mutations include point mutations, deletions, and insertions, which may occur in the [[Promoter (biology)|promoter]] region of a gene and affect its [[gene expression|expression]], or may occur in the gene's [[coding sequence]] and alter the function or stability of its [[protein]] product. Disruption of a single gene may also result from [[provirus|integration of genomic material]] from a [[DNA virus]] or [[retrovirus]], and resulting in the expression of ''viral'' oncogenes in the affected cell and its descendants.

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Replication of the enormous amount of data contained within the DNA of living cells will [[probability|probabilistically]] result in some errors (mutations). Complex error correction and prevention is built into the process, and safeguards the cell against cancer. If significant error occurs, the damaged cell can "self-destruct" through programmed cell death, termed [[apoptosis]]. If the error control processes fail, then the mutations will survive and be passed along to [[cell division|daughter cells]].

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Some environments make errors more likely to arise and propagate. Such environments can include the presence of disruptive substances called [[carcinogens]], repeated physical injury, heat, ionising radiation, or [[hypoxia (medical)|hypoxia]]<ref>{{cite journal | author = Nelson DA, Tan TT, Rabson AB, Anderson D, Degenhardt K, White E | title = Hypoxia and defective apoptosis drive genomic instability and tumorigenesis | journal = Genes & Development | volume = 18 | issue = 17 | pages = 2095–107 | year = 2004 | month = September | pmid = 15314031 | pmc = 515288 | doi = 10.1101/gad.1204904 }}</ref>

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The errors which cause cancer are ''self-amplifying'' and ''compounding'', for example:

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* A mutation in the error-correcting machinery of a cell might cause that cell and its children to accumulate errors more rapidly.

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* A further mutation in an oncogene might cause the cell to reproduce more rapidly and more frequently than its normal counterparts.

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* A further mutation may cause loss of a tumour suppressor gene, disrupting the apoptosis signalling pathway and resulting in the cell becoming immortal.

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* A further mutation in signaling machinery of the cell might send error-causing signals to nearby cells.

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The transformation of normal cell into cancer is akin to a [[chain reaction]] caused by initial errors, which compound into more severe errors, each progressively allowing the cell to escape the controls that limit normal tissue growth. This rebellion-like scenario becomes an undesirable [[survival of the fittest]], where the driving forces of [[evolution]] work against the body's design and enforcement of order. Once cancer has begun to develop, this ongoing process, termed ''clonal evolution'' drives progression towards more invasive stages.<ref name="pmid17109012">{{cite journal | author = Merlo LM, Pepper JW, Reid BJ, Maley CC | title = Cancer as an evolutionary and ecological process | journal = Nat. Rev. Cancer | volume = 6 | issue = 12 | pages = 924–35 | year = 2006 | month = December | pmid = 17109012 | doi = 10.1038/nrc2013 }}</ref>

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==Diagnosis==

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[[Image:Thorax pa peripheres Bronchialcarcinom li OF markiert.jpg|thumb|Chest x-ray showing lung cancer in the left lung.]]

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Most cancers are initially recognized either because of the appearance of signs or symptoms or through [[cancer screening|screening]]. Neither of these lead to a definitive diagnosis, which requires the examination of a tissue sample by a [[anatomical pathology|pathologist]]. People with suspected cancer are investigated with [[medical test]]s. These commonly include [[blood test]]s, [[X-ray]]s, [[X-ray computed tomography|CT scans]] and [[endoscopy]].

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===Classification===

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{{further2|[[List of cancer types]]|[[List of oncology-related terms]]}}

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Cancers are classified by the [[List of distinct cell types in the adult human body|type of cell]] that the tumor cells resemble and is therefore presumed to be the origin of the tumor. These types include:

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* [[Carcinoma]]: Cancers derived from [[epithelium|epithelial]] cells. This group includes many of the most common cancers, particularly in the aged, and include nearly all those developing in the [[breast cancer|breast]], [[prostate cancer|prostate]], [[lung cancer|lung]], [[pancreas]], and [[Colorectal cancer|colon]].

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* [[Sarcoma]]: Cancers arising from [[connective tissue]] (i.e. [[bone]], [[cartilage]], [[fat]], [[nerve]]), each of which develop from cells originating in [[mesenchyme|mesenchymal]] cells outside the bone marrow.

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* [[Lymphoma]] and [[leukemia]]: These two classes of cancer arise from hematopoietic ([[blood]]-forming) cells that leave the marrow and tend to mature in the lymph nodes and blood, respectively. Leukemia is the most common type of [[cancer in children]] accounting for about 30%.<ref>{{cite book |author=Varricchio, Claudette G. |title=A cancer source book for nurses |publisher=Jones and Bartlett Publishers |location=Boston |year=2004 |page=229 |isbn=0-7637-3276-1 |oclc= |url=http://books.google.co.jp/books?id=jkqdgZcF9qcC&pg=PA229}}</ref>

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* [[Germ cell tumor]]: Cancers derived from [[pluripotent]] cells, most often presenting in the [[testicular cancer|testicle]] or the [[ovarian cancer|ovary]] ([[seminoma]] and [[dysgerminoma]], respectively).

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* [[Blastoma]]: Cancers derived from immature "precursor" cells or embryonic tissue. Blastomas are more common in children than in older adults.

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Cancers are usually named using ''-carcinoma'', ''-sarcoma'' or ''-blastoma'' as a suffix, with the Latin or Greek word for the [[organ (anatomy)|organ]] or tissue of origin as the root. For example, cancers of the liver [[parenchyma]] arising from malignant epithelial cells is called ''[[hepatocarcinoma]]'', while a malignancy arising from primitive liver precursor cells is called a [[hepatoblastoma]], and a cancer arising from fat cells is called a ''[[liposarcoma]]''. For some common cancers, the English organ name is used. For example, the most common type of [[breast cancer]] is called ''[[mammary ductal carcinoma|ductal carcinoma of the breast]]''. Here, the adjective ''ductal'' refers to the appearance of the cancer under the microscope, which suggests that it has originated in the milk ducts.

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[[Benign tumor]]s (which are not cancers) are named using ''-oma'' as a suffix with the organ name as the root. For example, a benign tumor of smooth muscle cells is called a ''[[leiomyoma]]'' (the common name of this frequently occurring benign tumor in the uterus is ''[[uterine fibroid|fibroid]]''). Confusingly, some types of cancer use the ''-noma'' suffix, examples including [[melanoma]] and [[seminoma]].

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Some types of cancer are named for the size and shape of the cells under a microscope, such as [[giant cell carcinoma]], [[spindle cell carcinoma]], and [[small cell carcinoma]].

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===Pathology===

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The tissue [[medical diagnosis|diagnosis]] given by the pathologist indicates the type of cell that is proliferating, its [[histological grade]], genetic abnormalities, and other features of the tumor. Together, this information is useful to evaluate the [[prognosis]] of the patient and to choose the best treatment. [[Cytogenetics]] and [[immunohistochemistry]] are other types of testing that the pathologist may perform on the tissue specimen. These tests may provide information about the molecular changes (such as [[mutation]]s, [[fusion gene]]s, and numerical [[chromosome]] changes) that has happened in the cancer cells, and may thus also indicate the future behavior of the cancer (prognosis) and best treatment.

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−

Image:Breast cancer gross appearance.jpg|An invasive [[ductal carcinoma]] of the breast (pale area at the center) surrounded by spikes of whitish scar tissue and yellow fatty tissue.

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Image:Colon cancer 2.jpg|An invasive [[colorectal carcinoma]] (top center) in a [[colectomy]] specimen.

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Image:Lung cancer.jpg|A [[squamous cell carcinoma]] (the whitish tumor) near the [[bronchi]] in a lung specimen.

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Image:BreastCancer.jpg|A large invasive [[Mammary ductal carcinoma|ductal carcinoma]] in a [[mastectomy]] specimen.

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</gallery>

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==Prevention==

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Cancer prevention is defined as active measures to decrease the risk of cancer.<ref>{{cite web | url=http://www.mayoclinic.com/health/cancer-prevention/CA00024 | title=Cancer prevention: 7 steps to reduce your risk | publisher=[[Mayo Clinic]] | date=27 September 2008 | accessdate=30 January 2010}}</ref> The vast majority of cancer cases are due to environmental risk factors, and many, but not all, of these environmental factors are controllable lifestyle choices. Thus, cancer is considered a largely preventable disease.<ref name=Danaei>{{cite journal | author = Danaei G, Vander Hoorn S, Lopez AD, Murray CJ, Ezzati M | title = Causes of cancer in the world: comparative risk assessment of nine behavioural and environmental risk factors | journal = Lancet | volume = 366 | issue = 9499 | pages = 1784–93 | year = 2005 | pmid = 16298215 | doi = 10.1016/S0140-6736(05)67725-2 }}</ref> Greater than 30% of cancer deaths could be prevented by avoiding risk factors including: [[tobacco]], [[overweight]] / [[obesity]], an insufficient diet, [[physical inactivity]], [[alcohol]], [[sexually transmitted infection]]s, and [[air pollution]].<ref name="Cancer Cancer">{{cite web |url=http://www.who.int/mediacentre/factsheets/fs297/en/ |title=Cancer |work=World Health Organization |accessdate=9 January 2011}}</ref> Not all environmental causes are controllable, such as naturally occurring [[background radiation]], and other cases of cancer are caused through hereditary genetic disorders, and thus it is not possible to prevent all cases of cancer.

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===Dietary===

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While many dietary recommendations have been proposed to reduce the risk of cancer, few have significant supporting scientific evidence.<ref name=Diet11>{{cite journal | author = Wicki A, Hagmann, J | title = Diet and cancer. | journal = Swiss medical weekly | volume = 141 | issue = | pages = w13250 | year = 2011 | month = September | pmid = 21904992 | doi = 10.4414/smw.2011.13250 }}</ref> The primary dietary factors that increase risk are [[obesity]] and [[alcohol]] consumption; with a diet low in fruits and vegetables and high in red meat being implicated but not confirmed.<ref name="pmid22202045">{{cite journal | author = Cappellani A, Di Vita M, Zanghi A, Cavallaro A, Piccolo G, Veroux M, Berretta M, Malaguarnera M, Canzonieri V, Lo Menzo E | title = Diet, obesity and breast cancer: an update | journal = Front Biosci (Schol Ed) | volume = 4 | issue = | pages = 90–108 | year = 2012 | pmid = 22202045 | doi = }}</ref><ref name="pmid21119663">{{cite journal | author = Key TJ | title = Fruit and vegetables and cancer risk | journal = Br. J. Cancer | volume = 104 | issue = 1 | pages = 6–11 | year = 2011 | month = January | pmid = 21119663 | pmc = 3039795 | doi = 10.1038/sj.bjc.6606032 }}</ref> Consumption of [[coffee]] is associated with a reduced risk of [[liver cancer]].<ref name="pmid17484871">{{cite journal | author = Larsson SC, Wolk A | title = Coffee consumption and risk of liver cancer: a meta-analysis | journal = Gastroenterology | volume = 132 | issue = 5 | pages = 1740–5 | year = 2007 | month = May | pmid = 17484871 | doi = 10.1053/j.gastro.2007.03.044 }}</ref> Studies have linked consumption of red or processed meat to an increased risk of breast cancer, [[Colorectal cancer|colon cancer]], and [[pancreatic cancer]], a phenomenon which could be due to the presence of carcinogens in meats cooked at high temperatures.<ref name="pmid19838915">{{cite journal | author = Zheng W, Lee SA | title = Well-done meat intake, heterocyclic amine exposure, and cancer risk | journal = Nutr Cancer | volume = 61 | issue = 4 | pages = 437–46 | year = 2009 | pmid = 19838915 | pmc = 2769029 | doi = 10.1080/01635580802710741 }}</ref><ref name="pmid20374790">{{cite journal | author = Ferguson LR | title = Meat and cancer | journal = Meat Sci. | volume = 84 | issue = 2 | pages = 308–13 | year = 2010 | month = February | pmid = 20374790 | doi = 10.1016/j.meatsci.2009.06.032 }}</ref> Dietary recommendations for cancer prevention typically include an emphasis on vegetables, fruit, whole grains, and fish, and an avoidance of red meat, animal fats and refined carbohydrates. However, these recommendations are based on relatively limited evidence.<ref name=Diet11/>

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===Medication===

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The concept that medications can be used to prevent cancer is attractive, and evidence supports their use in a few defined circumstances.<ref>Holland Chp.33</ref> In the general population [[NSAIDs]] reduce the risk of [[colorectal cancer]] however due to the cardiovascular and gastrointestinal side effects they cause overall harm when used for prevention.<ref name="pmid17339623">{{cite journal | author = Rostom A, Dubé C, Lewin G, Tsertsvadze A, Barrowman N, Code C, Sampson M, Moher D | title = Nonsteroidal anti-inflammatory drugs and cyclooxygenase-2 inhibitors for primary prevention of colorectal cancer: a systematic review prepared for the U.S. Preventive Services Task Force | journal = Ann. Intern. Med. | volume = 146 | issue = 5 | pages = 376–89 | year = 2007 | month = March | pmid = 17339623 | doi = }}</ref> [[Aspirin]] has been found to reduce the risk of death from cancer by about 7%.<ref name="pmid21144578">{{cite journal | author = Rothwell PM, Fowkes FG, Belch JF, Ogawa H, Warlow CP, Meade TW | title = Effect of daily aspirin on long-term risk of death due to cancer: analysis of individual patient data from randomised trials | journal = Lancet | volume = 377 | issue = 9759 | pages = 31–41 | year = 2011 | month = January | pmid = 21144578 | doi = 10.1016/S0140-6736(10)62110-1 }}</ref> [[COX-2 inhibitor]] may decrease the rate of [[polyp]] formation in people with [[familial adenomatous polyposis]] however are associated with the same adverse effects as NSAIDs.<ref name="pmid20594533">{{cite journal | author = Cooper K, Squires H, Carroll C, Papaioannou D, Booth A, Logan RF, Maguire C, Hind D, Tappenden P | title = Chemoprevention of colorectal cancer: systematic review and economic evaluation | journal = Health Technol Assess | volume = 14 | issue = 32 | pages = 1–206 | year = 2010 | month = June | pmid = 20594533 | doi = 10.3310/hta14320 }}</ref> Daily use of [[tamoxifen]] or [[raloxifene]] has been demonstrated to reduce the risk of developing [[breast cancer]] in high-risk women.<ref name="pmid19020189">{{cite journal | author = Thomsen A, Kolesar JM | title = Chemoprevention of breast cancer | journal = Am J Health Syst Pharm | volume = 65 | issue = 23 | pages = 2221–8 | year = 2008 | month = December | pmid = 19020189 | doi = 10.2146/ajhp070663 }}</ref> The benefit verses harm for [[5-alpha-reductase inhibitor]] such as [[finasteride]] is not clear.<ref name="pmid18425978">{{cite journal | author = Wilt TJ, MacDonald R, Hagerty K, Schellhammer P, Kramer BS | title = Five-alpha-reductase Inhibitors for prostate cancer prevention | journal = Cochrane Database Syst Rev | volume = | issue = 2 | pages = CD007091 | year = 2008 | pmid = 18425978 | doi = 10.1002/14651858.CD007091 }}</ref>

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[[Vitamin]]s have not been found to be effective at preventing cancer,<ref name="pmid20939459">{{cite journal | author = | title = Vitamins and minerals: not for cancer or cardiovascular prevention | journal = Prescrire Int | volume = 19 | issue = 108 | pages = 182 | year = 2010 | month = August | pmid = 20939459 | doi = | url = http://english.prescrire.org/en/81/168/46461/0/2010/ArchiveNewsDetails.aspx?page=2 }}</ref> although low blood levels of [[vitamin D]] are correlated with increased cancer risk.<ref name="pmid16595781">{{cite journal | author = Giovannucci E, Liu Y, Rimm EB, Hollis BW, Fuchs CS, Stampfer MJ, Willett WC | title = Prospective study of predictors of vitamin D status and cancer incidence and mortality in men | journal = J. Natl. Cancer Inst. | volume = 98 | issue = 7 | pages = 451–9 | year = 2006 | month = April | pmid = 16595781 | doi = 10.1093/jnci/djj101 }}</ref><ref>{{cite web|url=http://www.cancer.org/docroot/NWS/content/NWS_1_1x_Vitamin_D_Has_Role_in_Colon_Cancer_Prevention.asp|title=Vitamin D Has Role in Colon Cancer Prevention|accessdate=27 July 2007 | archiveurl = http://web.archive.org/web/20061204052746/http://www.cancer.org/docroot/NWS/content/NWS_1_1x_Vitamin_D_Has_Role_in_Colon_Cancer_Prevention.asp| archivedate = 4 December 2006 }}</ref> Whether this relationship is causal and vitamin D supplementation is protective is not determined.<ref name="pmid16595770">{{cite journal | author = Schwartz GG, Blot WJ | title = Vitamin D status and cancer incidence and mortality: something new under the sun | journal = J. Natl. Cancer Inst. | volume = 98 | issue = 7 | pages = 428–30 | year = 2006 | month = April | pmid = 16595770 | doi = 10.1093/jnci/djj127 }}</ref> [[Beta-carotene]] supplementation has been found to increase [[lung cancer]] rates in those who are high risk.<ref name="pmid21738614">{{cite journal | author = Fritz H, Kennedy D, Fergusson D, Fernandes R, Doucette S, Cooley K, Seely A, Sagar S, Wong R, Seely D | title = Vitamin A and retinoid derivatives for lung cancer: a systematic review and meta analysis | journal = PLoS ONE | volume = 6 | issue = 6 | pages = e21107 | year = 2011 | pmid = 21738614 | pmc = 3124481 | doi = 10.1371/journal.pone.0021107 |bibcode = 2011PLoSO...6E1107F }}</ref> [[Folic acid]] supplementation has not been found effective in preventing colon cancer and may increase colon polyps.<ref name="pmid17551129">{{cite journal | author = Cole BF, Baron JA, Sandler RS, Haile RW, Ahnen DJ, Bresalier RS, McKeown-Eyssen G, Summers RW, Rothstein RI, Burke CA, Snover DC, Church TR, Allen JI, Robertson DJ, Beck GJ, Bond JH, Byers T, Mandel JS, Mott LA, Pearson LH, Barry EL, Rees JR, Marcon N, Saibil F, Ueland PM, Greenberg ER | title = Folic acid for the prevention of colorectal adenomas: a randomized clinical trial | journal = JAMA | volume = 297 | issue = 21 | pages = 2351–9 | year = 2007 | month = June | pmid = 17551129 | doi = 10.1001/jama.297.21.2351 }}</ref>

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===Vaccination===

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[[Vaccine]]s have been developed that prevent some infection by some viruses.<ref name=vacc_facts_nci>{{cite web | url=http://www.cancer.gov/cancertopics/factsheet/cancervaccine | title=Cancer Vaccine Fact Sheet | publisher=[[National Cancer Institute|NCI]] | date=8 June 2006 | accessdate=15 November 2008}}</ref> [[Human papillomavirus vaccine]] ([[Gardasil]] and [[Cervarix]]) decreases the risk of developing [[cervical cancer]].<ref name=vacc_facts_nci/> The [[hepatitis B vaccine]] prevents infection with hepatitis B virus and thus decreases the risk of liver cancer.<ref name=vacc_facts_nci/>

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==Screening==

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Unlike diagnosis efforts prompted by [[symptom]]s and [[medical sign]]s, cancer screening involves efforts to detect cancer after it has formed, but before any noticeable symptoms appear.<ref name=NIH>{{cite web |url=http://www.cancer.gov/cancertopics/pdq/screening/overview/Patient |title=What Is Cancer Screening? |work=National Cancer Institute |accessdate=}}</ref> This may involve [[physical examination]], [[blood test|blood]] or [[urine test]]s, or [[medical imaging]].<ref name=NIH/>

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Cancer screening is currently not possible for many types of cancers, and even when tests are available, they may not be recommended for everyone. ''[[Universal screening]]'' or ''mass screening'' involves screening everyone.<ref name=Wilson>Wilson JMG, Jungner G. (1968) [http://whqlibdoc.who.int/php/WHO_PHP_34.pdf Principles and practice of screening for disease.] Geneva:[[World Health Organization]]. Public Health Papers, #34.</ref> ''Selective screening'' identifies people who are known to be at higher risk of developing cancer, such as people with a family history of cancer.<ref name=Wilson /> Several factors are considered to determine whether the benefits of screening outweigh the risks and the costs of screening.<ref name=NIH/> These factors include:

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* Possible harms from the screening test: for example, X-ray images involve exposure to potentially harmful [[ionizing radiation]].

−

* The likelihood of the test correctly identifying cancer.

−

* The likelihood of cancer being present: Screening is not normally useful for rare cancers.

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* Possible harms from follow-up procedures.

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* Whether suitable treatment is available.

−

* Whether early detection improves treatment outcomes.

−

* Whether the cancer will ever need treatment.

−

* Whether the test is acceptable to the people: If a screening test is too burdensome (for example, being extremely painful), then people will refuse to participate.<ref name=Wilson />

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* Cost of the test.

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===Recommendations===

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The [[U.S. Preventive Services Task Force]] (USPSTF) strongly recommends [[cervical cancer]] screening in women who are [[sexually active]] and have a [[cervix]] at least until the age of 65.<ref>{{cite web |url=http://www.uspreventiveservicestaskforce.org/uspstf/uspscerv.htm |title=Screening for Cervical Cancer |year=2003 |work=[[U.S. Preventive Services Task Force]]}}</ref> They recommend that Americans be screened for [[colorectal cancer]] via [[fecal occult blood]] testing, [[sigmoidoscopy]], or [[colonoscopy]] starting at age 50 until age 75.<ref>{{cite web |url=http://www.uspreventiveservicestaskforce.org/uspstf/uspscolo.htm |title=Screening for Colorectal Cancer |year=2008 |work=[[U.S. Preventive Services Task Force]]}}</ref> There is insufficient evidence to recommend for or against screening for [[skin cancer]],<ref>{{cite web |url=http://www.uspreventiveservicestaskforce.org/uspstf/uspsskca.htm |title=Screening for Skin Cancer |year=2009 |work=[[U.S. Preventive Services Task Force]]}}</ref> [[oral cancer]],<ref>{{cite web |url=http://www.uspreventiveservicestaskforce.org/uspstf/uspsoral.htm |title=Screening for Oral Cancer |year=2004 |work=[[U.S. Preventive Services Task Force]]}}</ref> [[lung cancer]],<ref>{{cite web |url=http://www.uspreventiveservicestaskforce.org/uspstf/uspslung.htm |title=Lung Cancer Screening |year=2004 |work=[[U.S. Preventive Services Task Force]]}}</ref> or [[prostate cancer]] in men under 75.<ref name=USPSTFPr08>{{cite web |url=http://www.uspreventiveservicestaskforce.org/uspstf/uspsprca.htm |title=Screening for Prostate Cancer |year=2008 |work=[[U.S. Preventive Services Task Force]]}}</ref> Routine screening is not recommended for [[bladder cancer]],<ref>{{cite web |url=http://www.uspreventiveservicestaskforce.org/uspstf/uspsblad.htm |title=Screening for Bladder Cancer |year=2004 |work=[[U.S. Preventive Services Task Force]]}}</ref> [[testicular cancer]],<ref>{{cite web |url=http://www.uspreventiveservicestaskforce.org/uspstf/uspstest.htm |title=Screening for Testicular Cancer |year=2004 |work=[[U.S. Preventive Services Task Force]]}}</ref> [[ovarian cancer]],<ref>{{cite web |url=http://www.uspreventiveservicestaskforce.org/uspstf/uspsovar.htm |title=Screening for Ovarian Cancer |year=2004 |work=[[U.S. Preventive Services Task Force]]}}</ref> [[pancreatic cancer]],<ref>{{cite web |url=http://www.uspreventiveservicestaskforce.org/uspstf/uspspanc.htm |title=Screening for Pancreatic Cancer |year=2004 |work=[[U.S. Preventive Services Task Force]]}}</ref> or [[prostate cancer]].<ref name="USPSTF-20111007">{{cite web |last1=Chou |first1=Roger |last2=Croswell |first2=Jennifer M. |last3=Dana |first3=Tracy |last4=Bougatous |first4=Christina |last5=Blazina |first5=Ian |last6=Fu |first6=Rongwei |last7=Gleitsmann |first7=Ken |last8=Koenig |first8=Helen C. |last9=Lam |first9=Clarence |last10=Maltz |first10=Ashley |last11=Rugge |first11=J. Bruin |last12=Lin |first12=Kenneth |title=Screening for Prostate Cancer: A Review of the Evidence for the U.S. Preventive Services Task Force |url=http://www.uspreventiveservicestaskforce.org/uspstf12/prostate/prostateart.htm |date=7 October 2011 |publisher=[[United States Preventive Services Task Force]] |accessdate=8 October 2011}}</ref>

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The USPSTF recommends [[mammography]] for [[breast cancer]] screening every two years for those 50–74 years old; however, they do not recommend either [[breast self-examination]] or [[clinical breast examination]].<ref name=USPSTFBr09>{{cite web |url=http://www.uspreventiveservicestaskforce.org/uspstf/uspsbrca.htm |title=Screening for Breast Cancer |year=2009 |work=[[U.S. Preventive Services Task Force]]}}</ref> A 2011 [[Cochrane review]] came to slightly different conclusions with respect to breast cancer screening stating that routine mammography may do more harm than good.<ref name="CD001877">{{cite journal | author = Gøtzsche PC, Nielsen M | title = Screening for breast cancer with mammography | journal = Cochrane Database Syst Rev | volume = | issue = 1 | pages = CD001877 | year = 2011 | pmid = 21249649 | doi = 10.1002/14651858.CD001877.pub4 }}</ref>

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Japan screens for [[gastric cancer]] using [[photofluorography]] due to the high incidence there.<ref name=Epi11/>

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===Genetic testing===

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{| class="wikitable" style="float:right; margin-left:15px; text-align:center"

−

|-

−

! Gene

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! Cancer types

−

|-

−

| [[BRCA1]], [[BRCA2]]

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| Breast, ovarian, pancreatic

−

|-

−

| [[HNPCC]], [[MLH1]], [[MSH2]], [[MSH6]], [[PMS1]], [[PMS2]]

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| Colon, uterine, small bowel, stomach, urinary tract

−

|}

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[[Genetic testing]] for individuals at high-risk of certain cancers is recommended.<ref name=BRCA08>{{cite journal | author = Gulati AP, Domchek, SM | title = The clinical management of BRCA1 and BRCA2 mutation carriers | journal = Current oncology reports | volume = 10 | issue = 1 | pages = 47–53 | year = 2008 | month = Jan | pmid = 18366960 | doi = 10.1007/s11912-008-0008-9 }}</ref> Carriers of these mutations may than undergo enhanced surveillance, chemoprevention, or preventative surgery to reduce their subsequent risk.<ref name=BRCA08/>

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==Management==

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Many management options for cancer exist with the primary ones including [[surgery]], [[chemotherapy]], [[radiation therapy]], and [[palliative care]]. Which treatments are used depends upon the type, location and grade of the cancer as well as the person's health and wishes.

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===Palliative care===

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[[Palliative care]] refers to treatment which attempts to make the patient feel better and may or may not be combined with an attempt to attack the cancer. Palliative care includes action to reduce the physical, emotional, spiritual, and psycho-social distress experienced by people with cancer. Unlike treatment that is aimed at directly killing cancer cells, the primary goal of palliative care is to improve the patient's [[quality of life (healthcare)|quality of life]].

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Patients at all stages of cancer treatment need some kind of palliative care to comfort them. In some cases, [[Specialty (medicine)|medical specialty]] [[professional organizations]] recommend that patients and physicians respond to cancer only with palliative care and not with cancer-directed therapy.<ref name="ASCOfive">{{Citation |author1 = American Society of Clinical Oncology |author1-link = American Society of Clinical Oncology |date = |title = Five Things Physicians and Patients Should Question |publisher = [[American Society of Clinical Oncology]] |work = Choosing Wisely: an initiative of the [[ABIM Foundation]] |page = |url = http://choosingwisely.org/wp-content/uploads/2012/04/5things_12_factsheet_Amer_Soc_Clin_Onc.pdf |accessdate = August 14 2012}}</ref> Those cases have the following characteristics:<ref>

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*The American Society of Clinical Oncology made this recommendation based on various cancers. See {{Citation |author1 = American Society of Clinical Oncology |author1-link = American Society of Clinical Oncology |date = |title = Five Things Physicians and Patients Should Question |publisher = [[American Society of Clinical Oncology]] |work = Choosing Wisely: an initiative of the [[ABIM Foundation]] |page = |url = http://choosingwisely.org/wp-content/uploads/2012/04/5things_12_factsheet_Amer_Soc_Clin_Onc.pdf |accessdate = August 14 2012}}

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*for lung cancer, see {{cite PMID|21900105}} and {{cite PMID|20679538}}

−

*for breast cancer, see {{cite PMID|19200416}}

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*for colon cancer, see {{cite PMID|19755046}}

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*for other general statements see {{cite doi|10.1056/NEJMsb1013826}} and {{cite doi|10.1200/JCO.2010.33.1744}}</ref>

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#patient has low [[performance status]], corresponding with limited ability to care for oneself<ref name="ASCOfive"/>

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#patient received no benefit from prior [[Evidence-based medicine|evidence-based treatments]]<ref name="ASCOfive"/>

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#patient is ineligible to participate in any appropriate [[clinical trial]]<ref name="ASCOfive"/>

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#the physician sees no strong evidence that treatment would be effective<ref name="ASCOfive"/>

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Palliative care is often confused with [[hospice]] and therefore only involved when people approach [[End-of-life care|end of life]]. Like hospice care, palliative care attempts to help the person cope with the immediate needs and to increase the person's comfort. Unlike hospice care, palliative care does not require people to stop treatment aimed at prolonging their lives or curing the cancer.

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Multiple national [[medical guideline]]s recommend early palliative care for people whose cancer has produced distressing symptoms (pain, shortness of breath, fatigue, nausea) or who need help coping with their illness. In people who have metastatic disease when first diagnosed, oncologists should consider a palliative care consult immediately. Additionally, an oncologist should consider a palliative care consult in any patient they feel has a prognosis of less than 12 months even if continuing aggressive treatment.<ref>{{cite web|url=http://www.nccn.org/professionals/physician_gls/default.asp |title=NCCN Guidelines}}</ref><ref>{{cite web |url=http://www.nationalconsensusproject.org/guideline.pdf |title=Clinical Practice Guidelines for Quality Palliative Care |publisher = The National Consensus Project for Quality Palliative Care (NCP)}}</ref><ref>{{cite journal | author = Levy MH, Back, A, Bazargan, S, Benedetti, C, Billings, JA, Block, S, Bruera, E, Carducci, MA, Dy, S, Eberle, C, Foley, KM, Harris, JD, Knight, SJ, Milch, R, Rhiner, M, Slatkin, NE, Spiegel, D, Sutton, L, Urba, S, Von Roenn, JH, Weinstein, SM, National Comprehensive Cancer Network | title = Palliative care. Clinical practice guidelines in oncology | journal = Journal of the National Comprehensive Cancer Network: JNCCN | volume = 4 | issue = 8 | pages = 776–818 | year = 2006 | month = September | pmid = 16948956 | doi = }}</ref>

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===Surgery===

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Surgery is the primary method of treatment of most isolated solid cancers and may play a role in palliation and prolongation of survival. It is typically an important part of making the definitive diagnosis and [[cancer staging|staging the tumor]] as biopsies are usually required. In localized cancer surgery typically attempts to remove the entire mass along with, in certain cases, the [[lymph nodes]] in the area. For some types of cancer this is all that is needed to eliminate the cancer.<ref name=HollandTx40>Holland Chp. 40</ref>

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===Chemotherapy===

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[[Chemotherapy]] in addition to surgery has proven useful in a number of different cancer types including: [[breast cancer]], colorectal cancer, [[pancreatic cancer]], [[osteogenic sarcoma]], [[testicular cancer]], ovarian cancer, and certain lung cancers.<ref name=HollandTx40/> The effectiveness of chemotherapy is often limited by toxicity to other tissues in the body.

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===Radiation===

−

[[Radiation therapy]] involves the use of [[ionizing radiation]] in an attempt to either cure or improve the symptoms of cancer. It is used in about half of all cases and the radiation can be from either internal sources in the form of [[brachytherapy]] or external sources. Radiation is typically used in addition to surgery and or chemotherapy but for certain types of cancer such as early [[head and neck cancer]] may be used alone. For painful [[bone metastasis]] it has been found to be effective in about 70% of people.<ref name=H41>Holland Chp. 41</ref>

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===Alternative treatments===

−

[[Alternative cancer treatments|Complementary and alternative cancer treatments]] are a diverse group of health care systems, practices, and products that are not part of conventional medicine.<ref name="mnalt">{{cite journal | author = Cassileth BR, Deng G | title = Complementary and alternative therapies for cancer | journal = Oncologist | volume = 9 | issue = 1 | pages = 80–9 | year = 2004 | pmid = 14755017 | doi = 10.1634/theoncologist.9-1-80 }}</ref> "Complementary medicine" refers to methods and substances used along with conventional medicine, while "alternative medicine" refers to compounds used instead of conventional medicine.<ref>[http://nccam.nih.gov/health/whatiscam/#2 What Is CAM?] [[National Center for Complementary and Alternative Medicine]]. retrieved 3 February 2008.</ref> Most complementary and alternative medicines for cancer have not been rigorously studied or tested. Some alternative treatments have been investigated and shown to be ineffective but still continue to be marketed and promoted.<ref name="pmid15061600">{{cite journal | author = Vickers A | title = Alternative cancer cures: 'unproven' or 'disproven'? | journal = CA Cancer J Clin | volume = 54 | issue = 2 | pages = 110–8 | year = 2004 | pmid = 15061600 | doi = 10.3322/canjclin.54.2.110 }}</ref>

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==Prognosis==

−

Cancer has a reputation as a deadly disease. Taken as a whole, about half of people receiving treatment for invasive cancer (excluding [[carcinoma in situ]] and non-melanoma skin cancers) die from cancer or its treatment.<ref name=Epi11/> Survival is worse in the developing world.<ref name=Epi11/> However, the survival rates vary dramatically by type of cancer, with the range running from basically all people surviving to almost no one surviving.

−

Those who survive cancer are at increased risk of developing a second primary cancer at about twice the rate of those never diagnosed with cancer.<ref name="isbn1-55009-213-8" /> The increased risk is believed to be primarily due to the same risk factors that produced the first cancer, partly due to the treatment for the first cancer, and potentially related to better compliance with screening.<ref name="isbn1-55009-213-8">{{cite book| editor=Frei, Emil; Kufe, Donald W.; Holland, James F.|author=Rheingold, Susan; Neugut, Alfred; Meadows, Anna| title=Holland-Frei Cancer Medicine| edition = 6th| publisher=BC Decker| location=Hamilton, Ont| year=2003| page=2399| isbn=1-55009-213-8|chapterurl=http://www.ncbi.nlm.nih.gov/books/NBK20948/| chapter=156: Secondary Cancers: Incidence, Risk Factors, and Management| accessdate=5 November 2009}}</ref>

−

Predicting either short-term or long-term survival is difficult and depends on many factors. The most important factors are the particular kind of cancer and the patient's age and overall health. People who are [[wikt:frailty|frail]] with many other health problems have lower survival rates than otherwise healthy people. A [[centenarian]] is unlikely to survive for five years even if the treatment is successful. People who report a higher quality of life tend to survive longer.<ref>{{cite journal | author = Montazeri A | title = Quality of life data as prognostic indicators of survival in cancer patients: an overview of the literature from 1982 to 2008 | journal = Health Qual Life Outcomes | volume = 7 | issue = | pages = | year = 2009 | month = December | pmid = 20030832 | pmc = 2805623 | doi = 10.1186/1477-7525-7-102 }}</ref> People with lower quality of life may be affected by [[major depressive disorder]] and other complications from cancer treatment and/or disease progression that both impairs their quality of life and reduces their quantity of life. Additionally, patients with worse prognoses may be depressed or report a lower quality of life directly because they correctly perceive that their condition is likely to be fatal.

−

==Epidemiology==

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[[Image:Malignant neoplasms world map - Death - WHO2004.svg|thumb|Death rate from malignant cancer per 100,000 inhabitants in 2004.<ref>{{cite web |url=http://www.who.int/healthinfo/global_burden_disease/estimates_country/en/index.html |title=WHO Disease and injury country estimates |year=2009 |work=World Health Organization |accessdate=11 November 2009}}</ref>

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{{Multicol-end}} ]]

−

In 2008 approximately 12.7 million cancers were [[diagnosed]] (excluding [[non-melanoma skin cancer]]s and other non-invasive cancers) and 7.6 million people died of cancer worldwide.<ref name=Epi11>{{cite journal | author = Jemal A, Bray, F, Center, MM, Ferlay, J, Ward, E, Forman, D | title = Global cancer statistics | journal = CA: a cancer journal for clinicians | volume = 61 | issue = 2 | pages = 69–90 | year = 2011 | month = February | pmid = 21296855 | doi = 10.3322/caac.20107 }}</ref> Cancers as a group account for approximately 13% of all deaths each year with the most common being: [[lung cancer]] (1.4 million deaths), [[stomach cancer]] (740,000 deaths), [[liver cancer]] (700,000 deaths), [[colorectal cancer]] (610,000 deaths), and [[breast cancer]] (460,000 deaths).<ref name="WHO">{{cite web | last =WHO | authorlink =World Health Organization | title =Cancer | publisher =World Health Organization |month=October | year=2010 | url =http://www.who.int/mediacentre/factsheets/fs297/en/ | accessdate =5 January 2011}}</ref> This makes invasive cancer the leading cause of death in the [[developed world]] and the second leading cause of death in the [[developing world]].<ref name=Epi11/> Over half of cases occur in the developing world.<ref name=Epi11/>

−

Global cancer rates have been increasing primarily due to an aging population and lifestyle changes in the developing world.<ref name=Epi11/> The most significant [[risk factor]] for developing cancer is old age.<ref name=Coleman>{{cite book|author=Coleman, William B. and Rubinas, Tara C.|editor=Tsongalis, Gregory J. and Coleman, William L.|title=Molecular Pathology: The Molecular Basis of Human Disease|publisher=Elsevier Academic Press|location=Amsterdam|year=2009|page=66|chapter=4|isbn=0-12-374419-9|oclc=}}</ref> Although it is possible for cancer to strike at any age, most people who are diagnosed with invasive cancer are over the age of 65.<ref name=Coleman /> According to cancer researcher [[Robert A. Weinberg]], "If we lived long enough, sooner or later we all would get cancer."<ref name=Weinberg>{{cite news| url = http://www.nytimes.com/2010/12/28/health/28cancer.html| title = Unearthing Prehistoric Tumors, and Debate| newspaper = [[The New York Times]]| date = 28 December 2010| author = Johnson, George}}</ref> Some of the association between aging and cancer is attributed to [[immunosenescence]],<ref>{{cite journal | author = Pawelec G, Derhovanessian, E, Larbi, A | title = Immunosenescence and cancer | journal = Critical reviews in oncology/hematology | volume = 75 | issue = 2 | pages = 165–72 | year = 2010 | month = Aug | pmid = 20656212 | doi = 10.1016/j.critrevonc.2010.06.012 }}</ref> errors accumulated in [[DNA]] over a lifetime,<ref>{{cite book

−

|author=Alberts, B, Johnson A, Lewis J, et al.

−

|title=Molecular biology of the cell

−

|publisher=Garland Science

−

|location=New York

−

|year=2002

−

|edition=4th

−

|chapter=The Preventable Causes of Cancer

−

|isbn=0-8153-4072-9

−

|url=http://www.ncbi.nlm.nih.gov/books/NBK26897/

−

|quote=A certain irreducible background incidence of cancer is to be expected regardless of circumstances: mutations can never be absolutely avoided, because they are an inescapable consequence of fundamental limitations on the accuracy of DNA replication, as discussed in Chapter 5. If a human could live long enough, it is inevitable that at least one of his or her cells would eventually accumulate a set of mutations sufficient for cancer to develop.

−

|oclc=

−

|doi= }}</ref> and age-related changes in the endocrine system.<ref>{{cite journal | author = Anisimov VN, Sikora, E, Pawelec, G | title = Relationships between cancer and aging: a multilevel approach | journal = Biogerontology | volume = 10 | issue = 4 | pages = 323–38 | year = 2009 | month = Aug | pmid = 19156531 | doi = 10.1007/s10522-008-9209-8 }}</ref>

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Some slow-growing cancers are particularly common. [[Autopsy]] studies in Europe and Asia have shown that up to 36% of people have undiagnosed and apparently harmless [[thyroid cancer]] at the time of their deaths, and that 80% of men develop [[prostate cancer]] by age 80.<ref>{{cite book| author = Fraumeni, Joseph F.; Schottenfeld, David; Marshall, James M.| title = Cancer epidemiology and prevention| publisher = Oxford University Press| location = Oxford [Oxfordshire]| year = 2006| page = 977| isbn = 0-19-514961-0| oclc =}}</ref><ref>{{cite book| author = Bostwick, David G.; Eble, John N.| title = Urological Surgical Pathology| publisher = Mosby| location = St. Louis| year = 2007| page = 468| isbn = 0-323-01970-6| oclc =}}</ref> As these cancers did not cause the person's death, identifying them would have represented [[overdiagnosis]] rather than useful medical care.

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The three most common [[childhood cancer]]s are [[leukemia]] (34%), [[brain tumor]]s (23%), and [[lymphoma]]s (12%).<ref name=Euro10>{{cite journal | author = Kaatsch P, Sikora, E, Pawelec, G | title = Epidemiology of childhood cancer | journal = Cancer treatment reviews | volume = 36 | issue = 4 | pages = 277–85 | year = 2010 | month = June | pmid = 20231056 | doi = 10.1016/j.ctrv.2010.02.003 }}</ref> Rates of childhood cancer have increased by 0.6% per year between 1975 to 2002 in the United States<ref>{{cite journal | author = Ward EM, Thun, MJ, Hannan, LM, Jemal, A | title = Interpreting cancer trends | journal = Annals of the New York Academy of Sciences | volume = 1076 | issue = | pages = 29–53 | year = 2006 | month = Sep | pmid = 17119192 | doi = 10.1196/annals.1371.048 | bibcode = 2006NYASA1076...29W }}</ref> and by 1.1% per year between 1978 and 1997 in Europe.<ref name=Euro10/>

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==History==

−

[[File:Clara Jacobi-Tumor.jpg|thumb|[[Engraving]] with two views of a Dutch woman who had a tumor removed from her neck in 1689.]]

−

The earliest written record regarding cancer is from 3000 BC in the Egyptian [[Edwin Smith Papyrus]] and describes cancer of the breast.<ref name=Hist1>{{cite journal | author = Hajdu SI, Thun, MJ, Hannan, LM, Jemal, A | title = A note from history: landmarks in history of cancer, part 1. | journal = Cancer | volume = 117 | issue = 5 | pages = 1097–102 | year = 2011 | month = March | pmid = 20960499 | doi = 10.1002/cncr.25553 }}</ref> Cancer however has existed for all of human history.<ref name=Hist1/> [[Hippocrates]] (ca. 460 BC – ca. 370 BC) described several kinds of cancer, referring to them with the [[Greek language|Greek]] word ''carcinos'' ([[crab]] or [[crayfish]]).<ref name=Hist1/> This name comes from the appearance of the cut surface of a solid malignant tumour, with "the veins stretched on all sides as the animal the crab has its feet, whence it derives its name".<ref>Paul of Aegina, 7th Century AD, quoted in {{cite web| first = Ralph W.| last = Moss| title = Galen on Cancer| url = http://www.cancerdecisions.com/speeches/galen1989.html| archiveurl = http://web.archive.org/web/20110716111312/http://www.cancerdecisions.com/speeches/galen1989.html| archivedate = 16 July 2011| publisher = CancerDecisions| year = 2004}} Referenced from Michael Shimkin, Contrary to Nature, Washington, D.C.: Superintendent of Document, DHEW Publication No. (NIH) 79-720, p. 35.</ref> [[Aulus Cornelius Celsus|Celsus]] (ca. 25 BC – 50 AD) translated ''carcinos'' into the [[Latin]] ''cancer'', also meaning crab and recommended surgery as treatment.<ref name=Hist1/> [[Galen]] (2nd century AD) disagreed with the use of surgery and recommended [[purgatives]] instead.<ref name=Hist1/> These recommendations largely stood for 1000 years.<ref name=Hist1/>

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In the 15th, 16th and 17th centuries, it became more acceptable for doctors to [[autopsy|dissect bodies]] to discover the cause of death.<ref name=Hist2>{{cite journal | author = Hajdu SI, Thun, MJ, Hannan, LM, Jemal, A | title = A note from history: landmarks in history of cancer, part 2. | journal = Cancer | volume = 117 | issue = 12 | pages = 2811–20 | year = 2011 | month = June | pmid = 21656759 | doi = 10.1002/cncr.25825 }}</ref> The German professor [[Wilhelm Fabry]] believed that breast cancer was caused by a milk clot in a mammary duct. The Dutch professor [[Francois de la Boe Sylvius]], a follower of [[Descartes]], believed that all disease was the outcome of chemical processes, and that acidic [[lymph]] fluid was the cause of cancer. His contemporary [[Nicolaes Tulp]] believed that cancer was a poison that slowly spreads, and concluded that it was [[infectious disease|contagious]].<ref>{{cite book|last=Yalom|first=Marilyn|title=A history of the breast|year=1998|publisher=Ballantine Books|location=New York|isbn=0-679-43459-3|edition=1st Ballantine Books ed.}}</ref>

−

The physician John Hill described tobacco snuff as the cause of nose cancer in 1761.<ref name=Hist2/> This was followed by the report in 1775 by British surgeon [[Percivall Pott]] that cancer of the [[scrotum]] was a common disease among [[chimney sweep]]s.<ref>{{cite journal | author = Hajdu SI, Thun, MJ, Hannan, LM, Jemal, A | title = A note from history: Landmarks in history of cancer, part 3. | journal = Cancer | volume = 118 | issue = 4 | pages = 1155–68 | year = 2011 | month = July | pmid = 21751192 | doi = 10.1002/cncr.26320 }}</ref> With the widespread use of the microscope in the 18th century, it was discovered that the 'cancer poison' spread from the primary tumor through the lymph nodes to other sites ("[[metastasis]]"). This view of the disease was first formulated by the English surgeon [[Campbell De Morgan]] between 1871 and 1874.<ref>{{cite journal | author = Grange JM, Stanford JL, Stanford CA | title = Campbell De Morgan's 'Observations on cancer', and their relevance today | journal = Journal of the Royal Society of Medicine | volume = 95 | issue = 6 | pages = 296–9 | year = 2002 | pmid = 12042378 | pmc = 1279913 | doi = 10.1258/jrsm.95.6.296 }}</ref>

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==Society and culture==

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Though many diseases (such as [[heart failure]]) may have a worse prognosis than most cases of cancer, cancer is the subject of widespread fear and taboos. The [[euphemism]], "after a long illness" is still commonly used (2012), reflecting an apparent [[social stigma|stigma]].<ref>{{Cite news

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| first = Barbara

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| last = Ehrenreich

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| authorlink = Barbara Ehrenreich

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| title = Welcome to Cancerland

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| newspaper = [[Harper's Magazine]]

−

| date = November 2001

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| issn = 0017-789X

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| url = http://www.barbaraehrenreich.com/cancerland.htm}}</ref> This deep belief that cancer is necessarily a difficult and usually deadly disease is reflected in the systems chosen by society to compile cancer statistics: the most common form of cancer—non-melanoma [[skin cancer]]s, accounting for about one-third of all cancer cases worldwide, but very few deaths<ref name="Bolognia">{{cite book |author=Rapini, Ronald P.; Bolognia, Jean L.; Jorizzo, Joseph L. |title=Dermatology: 2-Volume Set |publisher=Mosby |location=St. Louis |year=2007 |pages= |isbn=1-4160-2999-0 |oclc= |doi=}}</ref><ref>{{cite web

−

| title = Skin cancers

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| url = http://www.who.int/uv/faq/skincancer/en/index1.html

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| publisher = World Health Organization

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| accessdate = 19 January 2011}}</ref>—are excluded from cancer statistics specifically because they are easily treated and almost always cured, often in a single, short, outpatient procedure.<ref>{{cite book

−

|author=McCulley, Michelle; Greenwell, Pamela

−

|title=Molecular therapeutics: 21st-century medicine

−

|publisher=J. Wiley

−

|location=London

−

|year=2007

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|page= 207

−

|isbn=0-470-01916-6

−

|oclc=}}</ref>

−

Cancer is regarded as a disease that must be "fought" to end the "civil insurrection"; a [[War on Cancer]] has been declared. Military metaphors are particularly common in descriptions of cancer's human effects, and they emphasize both the parlous state of the affected individual's health and the need for the individual to take immediate, decisive actions himself, rather than to delay, to ignore, or to rely entirely on others caring for him. The military metaphors also help rationalize radical, destructive treatments.<ref name=Gwyn>{{cite book

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| author=Gwyn, Richard

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| editor=Cameron, Lynne; Low, Graham

−

| title=Researching and applying metaphor

−

| publisher=Cambridge University Press

−

| location=Cambridge, UK

−

| year=1999

−

| chapter=10

−

| isbn=0-521-64964-1}}</ref><ref>{{cite book

−

| author=Sulik, Gayle

−

| title=Pink Ribbon Blues: How Breast Cancer Culture Undermines Women's Health

−

| publisher=Oxford University Press

−

| location=New York

−

| year=2010

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| oclc = 535493589

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| isbn=0-19-974045-3

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| pages=78–89}}</ref>

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In the 1970s, a relatively popular [[alternative cancer treatment]] was a specialized form of [[talk therapy]], based on the idea that cancer was caused by a bad attitude.<ref name=Olson /> People with a "cancer personality"—depressed, repressed, self-loathing, and afraid to express their emotions—were believed to have manifested cancer through subconscious desire. Some psychotherapists said that treatment to change the patient's outlook on life would cure the cancer.<ref name=Olson /> Among other effects, this belief allows society to [[blame the victim]] for having caused the cancer (by "wanting" it) or having prevented its cure (by not becoming a sufficiently happy, fearless, and loving person).<ref name=Ehrenreich /> It also increases patients' anxiety, as they incorrectly believe that natural emotions of sadness, anger or fear shorten their lives.<ref name=Ehrenreich /> The idea was excoriated by the notoriously outspoken [[Susan Sontag]], who published ''[[Illness as Metaphor]]'' while recovering from treatment for [[breast cancer]] in 1978.<ref name=Olson>{{cite book

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| author=Olson, James Stuart

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| title=Bathsheba's Breast: Women, Cancer and History

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| publisher=The Johns Hopkins University Press

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| location=Baltimore

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| year=2002

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| pages = 145–170

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| oclc = 186453370

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| isbn=0-8018-6936-6}}</ref> Although the original idea is now generally regarded as nonsense, the idea partly persists in a reduced form with a widespread, but incorrect, belief that deliberately cultivating a habit of [[positive thinking]] will increase survival.<ref name=Ehrenreich>{{cite book

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|author=Ehrenreich, Barbara

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|title=Bright-sided: How the Relentless Promotion of Positive Thinking Has Undermined America

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|publisher=Metropolitan Books

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|location=New York

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|year=2009

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|pages=15–44

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|isbn=0-8050-8749-4

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|oclc=}}</ref> This notion is particularly strong in [[breast cancer culture]].<ref name=Ehrenreich />

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In 2007, the overall costs of cancer in the U.S. — including treatment and indirect mortality expenses (such as lost productivity in the workplace) — was estimated to be $226.8 billion. In 2009, 32% of Hispanics and 10% of children 17 years old or younger lacked health insurance; "uninsured patients and those from ethnic minorities are substantially more likely to be diagnosed with cancer at a later stage, when treatment can be more extensive and more costly."<ref>{{cite web|url = http://journalistsresource.org/studies/society/health/cancer-facts-figures-2012/ |title = Cancer Facts and Figures 2012 |publisher = Journalist's Resource.org }}</ref>

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==Research==

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Because cancer is a class of diseases,<ref name=WhatIsCancerNCI>{{cite web| url=http://www.cancer.gov/cancertopics/what-is-cancer| title=What Is Cancer?| publisher=[[National Cancer Institute]]| accessdate=17 August 2009}}</ref><ref>{{cite web|url=http://www.atsdr.cdc.gov/COM/cancer-fs.html| title=Cancer Fact Sheet| publisher=Agency for Toxic Substances & Disease Registry|date=30 August 2002| accessdate=17 August 2009}}</ref> it is unlikely that there will ever be a single "[[cure for cancer]]" any more than there will be a single treatment for all [[infectious disease]]s.<ref>{{cite web| url=http://www.livescience.com/health/060919_bad_cancer.html|title=Exciting New Cancer Treatments Emerge Amid Persistent Myths| last=Wanjek| first= Christopher| date=16 September 2006|accessdate=17 August 2009}}</ref> [[Angiogenesis inhibitors]] were once thought to have potential as a "[[silver bullet]]" treatment applicable to many types of cancer, but this has not been the case in practice.<ref>{{cite journal | author = Hayden EC, Thun, MJ, Hannan, LM, Jemal, A | title = Cutting off cancer's supply lines | journal = Nature | volume = 458 | issue = 7239 | pages = 686–687 | year = 2009 | month = April | pmid = 19360048 | doi = 10.1038/458686b }}</ref>

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[[Experimental cancer treatment]]s are treatments that are being studied to see whether they work. Typically, these are studied in [[clinical trial]]s to compare the proposed treatment to the best existing treatment. They may be entirely new treatments, or they may be treatments that have been used successfully in one type of cancer, and are now being tested to see whether they are effective in another type.<ref>{{cite journal | author = Sleigh SH, Barton CL | title = Repurposing Strategies for Therapeutics | journal = Pharm Med | volume = 24 | issue = 3 | pages = 151–159 | year = 2010 | pmid = | doi = 10.2165/11536770-000000000-00000 }}</ref> More and more, such treatments are being developed alongside companion diagnostic tests to target the right drugs to the right patients, based on their individual biology.<ref>{{cite journal | author = Winther H, Jorgensen JT | title = Drug-Diagnostic Co-Development in Cancer | journal = Pharm Med | volume = 24 | issue = 6 | pages = 363–375 | year = 2010 | pmid = | doi = 10.2165/11586320-000000000-00000 }}</ref>

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Cancer research is the intense scientific effort to understand disease processes and discover possible therapies.

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Research about cancer causes focuses on the following issues:

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* Agents (e.g. viruses) and events (e.g. mutations) which cause or facilitate genetic changes in cells destined to become cancer.

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* The precise nature of the genetic damage, and the genes which are affected by it.

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* The consequences of those genetic changes on the biology of the cell, both in generating the defining properties of a cancer cell, and in facilitating additional genetic events which lead to further progression of the cancer.

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The improved understanding of [[molecular biology]] and [[cellular biology]] due to cancer research has led to a number of new treatments for cancer since U.S. President Nixon declared the "[[War on Cancer]]" in 1971. Since then, the U.S. has spent over $200 billion on cancer research, including resources from the public and private sectors and foundations.<ref>{{cite web |author=Sharon Begley | url=http://www.newsweek.com/id/157548/page/2 |title=Rethinking the War on Cancer |date=16 September 2008 | work=Newsweek |accessdate=8 September 2008}}</ref> During that time, the country has seen a five percent decrease in the cancer death rate (adjusting for size and age of the population) between 1950 and 2005.<ref>{{cite news|url=http://www.nytimes.com/2009/04/24/health/policy/24cancer.html |title=Advances Elusive in the Drive to Cure Cancer |last=Kolata|first=Gina|authorlink=Gina Kolata|date=23 April 2009 |work=[[The New York Times]]|accessdate=5 May 2009}}</ref>

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==Pregnancy==

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Because cancer is largely a disease of older adults, it is not common in pregnant women. Cancer affects approximately 1 in 1,000 pregnant women.<ref name=yarbro /> The most common cancers found during pregnancy are the same as the most common cancers found in non-pregnant women during childbearing ages: breast cancer, cervical cancer, leukemia, lymphoma, melanoma, ovarian cancer, and colorectal cancer.<ref name=yarbro />

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Diagnosing a new cancer in a pregnant woman is difficult, in part because any symptoms are commonly assumed to be a normal discomfort associated with pregnancy.<ref name=yarbro /> As a result, cancer is typically discovered at a somewhat later stage than average in many pregnant or recently pregnant women. Some imaging procedures, such as [[MRI]]s (magnetic resonance imaging), [[CT scan]]s, ultrasounds, and [[mammogram]]s with fetal shielding are considered safe during pregnancy; some others, such as [[PET scan]]s are not.<ref name=yarbro />

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Treatment is generally the same as for non-pregnant women.<ref name=yarbro /> However, radiation and radioactive drugs are normally avoided during pregnancy, especially if the fetal dose might exceed 100 cGy. In some cases, some or all treatments are postponed until after birth if the cancer is diagnosed late in the pregnancy. Early deliveries to speed the start of treatment are not uncommon. Surgery is generally safe, but pelvic surgeries during the first trimester may cause miscarriage. Some treatments, especially certain chemotherapy drugs given during the [[first trimester]], increase the risk of [[birth defect]]s and [[pregnancy loss]] (spontaneous abortions and stillbirths).<ref name=yarbro />

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Elective [[abortion]]s are not required and, for the most common forms and stages of cancer, do not improve the likelihood of the mother surviving or being cured.<ref name=yarbro /> In a few instances, such as advanced uterine cancer, the pregnancy cannot be continued, and in others, such as an acute leukemia discovered early in pregnancy, the pregnant woman may choose to have abortion so that she can begin aggressive chemotherapy without worrying about birth defects.<ref name=yarbro />

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Some treatments may interfere with the mother's ability to give birth vaginally or to breastfeed her baby.<ref name=yarbro /> Cervical cancer may require birth by Caesarean section. Radiation to the breast reduces the ability of that breast to produce milk and increases the risk of [[mastitis]]. Also, when chemotherapy is being given after birth, many of the drugs pass through breast milk to the baby, which could harm the baby.<ref name=yarbro>{{cite book

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| title = Cancer nursing: principles and practice

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| editor = Connie Henke Yarbro, Debra Wujcik, Barbara Holmes Gobel

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| edition = 7

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| publisher= Jones & Bartlett Publishers

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| year = 2011

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| isbn = 978-1-4496-1829-2

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| pages = 901–905}}</ref>

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==Other animals==

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In non-humans, a few types of [[transmissible cancer]] have been described, wherein the cancer spreads between animals by transmission of the tumor cells themselves. This phenomenon is seen in dogs with [[Sticker's sarcoma]], also known as canine transmissible venereal tumor,<ref name="pmid16901782">{{cite journal | author = Murgia C, Pritchard JK, Kim SY, Fassati A, Weiss RA | title = Clonal origin and evolution of a transmissible cancer | journal = Cell | volume = 126 |issue = 3 | pages = 477–87 | year = 2006 | month = August | pmid = 16901782 | pmc = 2593932 | doi = 10.1016/j.cell.2006.05.051 }}</ref> as well as [[devil facial tumour disease]] in [[Tasmanian devil]]s.

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==Notes==

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;References

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* {{cite book|last=Holland|first=James F.|title=Holland-Frei cancer medicine.|year=2009|publisher=McGraw-Hill Medical|location=New York|isbn=978-1-60795-014-1|edition=8th ed.}}

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==Further reading==

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* {{cite book|last=Kleinsmith|first=Lewis J.|title=Principles of cancer biology|url=http://books.google.com/books?id=LKVrAAAAMAAJ|year=2006|publisher=Pearson Benjamin Cummings|isbn=978-0-8053-4003-7}}

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* {{cite book|last=Mukherjee|first=Siddhartha|authorlink=Siddhartha Mukherjee|title=[[The Emperor of All Maladies: A Biography of Cancer]]|accessdate=6 September 2011|date=16 November 2010|publisher=Simon and Schuster|isbn=978-1-4391-0795-9}}

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* {{cite book|last1=Pazdur|first1=Richard|author2=et al.|title=Cancer Management: A Multidisciplinary Approach|url=http://books.google.com/books?id=wbLnPAAACAAJ|date=May 2009|publisher=Cmp United Business Media|isbn=978-1-891483-62-2}} [http://www.cancernetwork.com/cancer-management-11 (online at cancernetwork.com)]

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* {{cite book|last=Tannock|first=Ian|title=The basic science of oncology|url=http://books.google.com/books?id=Bb4F4pj2BdYC|year=2005|publisher=McGraw-Hill Professional|isbn=978-0-07-138774-3}}

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* {{cite book |author=Manfred Schwab |title=Encyclopedia of Cancer (4 Volume Set) |publisher=Springer |location=Berlin |year=2008 |isbn=3-540-36847-7}}

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==External links==

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* {{dmoz|Health/Conditions_and_Diseases/Cancer/}}

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[[Category:Cancer| ]]

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[[Category:Aging-associated diseases]]

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[[Category:Types of cancer| ]]

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[[Category:Occupational safety and health]]

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[[Category:Oncology|*Cancer]]

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[[Category:Pathology]]

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[[Category:Types of neoplasia|*Cancer]]

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Changes: Cancer

Latest revision as of 22:35, 3 April 2016

@@ Line 1: / Line 1: @@
+#REDIRECT [[Cancer]]
-{{Other uses}}
-{{sprotected2}}{{pp-move-indef}}
-{{Use dmy dates|date=June 2012}}
-{{Infobox disease
-| Name = Cancer
-| Image = Tumor_Mesothelioma2_legend.jpg
-| Caption = A coronal [[CT scan]] showing a malignant [[mesothelioma]]<br />Legend: →&nbsp;[[tumor]]&nbsp;←, ✱&nbsp;central [[pleural effusion]], 1 & 3&nbsp;[[lungs]], 2&nbsp;[[Vertebral column|spine]], 4&nbsp;[[ribs]], 5&nbsp;[[aorta]], 6&nbsp;[[spleen]], 7 & 8&nbsp;[[kidneys]], 9&nbsp;[[liver]].
-| DiseasesDB = 28843
-| ICD10 ={{ICD10|C|00}}—{{ICD10|C|97}}
-| ICD9 = {{ICD9|140}}—{{ICD9|239}}
-| ICDO =
-| MedlinePlus = 001289
-| eMedicineSubj =
-| eMedicineTopic =
-| MeshID = D009369
-}}
-'''Cancer''' {{IPAc-en|audio=en-us-cancer.ogg|ˈ|k|æ|n|s|ər}}, known medically as a [[malignancy|malignant]] [[neoplasm]], is a broad group of various [[disease]]s, all involving unregulated cell growth. In cancer, [[cell (biology)|cells]] divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also [[metastasis|spread]] to more distant parts of the body through the [[lymph|lymphatic system]] or [[blood]]stream. Not all tumors are cancerous. [[Benign tumor]]s do not grow uncontrollably, do not invade neighboring tissues, and do not spread throughout the body. There are over 200 different known cancers that afflict humans.<ref>{{cite web |url=http://cancerhelp.cancerresearchuk.org/about-cancer/cancer-questions/how-many-different-types-of-cancer-are-there |title=How many different types of cancer are there? : Cancer Research UK : CancerHelp UK |format= |work= |accessdate=11 May 2012}}</ref>
-<!--Cause -->
-Determining what causes cancer is complex. Many things are known to increase the risk of cancer, including [[tobacco]] use, certain [[infection]]s, [[radiation]], [[lack of physical activity]], [[obesity]], and environmental pollutants.<ref name=Enviro2008>{{cite journal | author = Anand P, Kunnumakkara AB, Kunnumakara AB, Sundaram C, Harikumar KB, Tharakan ST, Lai OS, Sung B, Aggarwal BB | title = Cancer is a preventable disease that requires major lifestyle changes | journal = Pharm. Res. | volume = 25 | issue = 9 | pages = 2097–116 | year = 2008 | month = September | pmid = 18626751 | pmc = 2515569 | doi = 10.1007/s11095-008-9661-9 }}</ref> These can directly damage genes or combine with existing genetic faults within cells to cause the disease.<ref name="Kinz">{{cite book | author = Kinzler, Kenneth W.; Vogelstein, Bert | title = The genetic basis of human cancer | edition = 2nd, illustrated, revised| publisher = McGraw-Hill, Medical Pub. Division | location = New York | year = 2002 | page = 5| isbn = 978-0-07-137050-9 | url = http://books.google.com/?id=pYG09OPbXp0C| chapter=Introduction |chapterurl=http://books.google.co.uk/books?id=pYG09OPbXp0C&pg=PA5}}</ref> Approximately five to ten percent of cancers are entirely hereditary.
-<!--Diagnosis, Treatment, Epidemiology -->
-Cancer can be detected in a number of ways, including the presence of certain [[cancer symptoms|signs and symptoms]], [[cancer screening|screening tests]], or [[medical imaging]]. Once a possible cancer is detected it is diagnosed by [[histology|microscopic examination]] of a [[biopsy|tissue sample]]. Cancer is usually treated with [[chemotherapy]], [[radiation therapy]] and [[surgery]]. The chances of surviving the disease vary greatly by the type and location of the cancer and the extent of disease at the start of treatment. While cancer can affect people of all ages, and a few types of cancer are more common in children, the risk of developing cancer generally increases with age. In 2007, cancer caused about 13% of [[causes of death|all human deaths]] worldwide (7.9&nbsp;million). Rates are rising as more people live to an old age and as mass lifestyle changes occur in the developing world.<ref name=Epi11/>
-==Signs and symptoms==
-{{Main|Cancer signs and symptoms}}
-[[Image:Symptoms of cancer metastasis.svg|thumb|Symptoms of [[cancer metastasis]] depend on the location of the tumor.]]
-When cancer begins it invariably produces no symptoms with signs and symptoms only appearing as the mass continues to grow or [[ulcer (dermatology)|ulcerates]].<!--<ref name=Card10/> --> The findings that result depends on the type and location of the cancer.<!--<ref name=Card10/> --> Few symptoms are [[non-specific symptom|specific]], with many of them also frequently occurring in individuals who have other conditions.<!--<ref name=Card10/> --> Cancer is the new "[[the great imitator|great imitator]]".<!--<ref name=Card10/> --> Thus it is not uncommon for people diagnosed with cancer to have been treated for other diseases to which it was assumed their symptoms were due.<ref name=Card10>Holland Chp. 1</ref>
-===Local effects===
-Local symptoms may occur due to the mass of the tumor or its ulceration.<!--<ref name=Card10/> --> For example, mass effects from [[lung cancer]] can cause blockage of the [[bronchus]] resulting in [[cough]] or [[pneumonia]]; [[esophageal cancer]] can cause narrowing of the esophagus, making it difficult or painful to swallow; and [[colorectal cancer]] may lead to narrowing or blockages in the bowel, resulting in changes in bowel habits.<!--<ref name=Card10/> --> Masses of breast or testicles may be easily felt.<!--<ref name=Card10/> --> [[ulcer (dermatology)|Ulceration]] can cause bleeding which, if it occurs in the lung, will lead to [[hemoptysis|coughing up blood]], in the bowels to [[anemia]] or [[Lower gastrointestinal bleeding|rectal bleeding]], in the bladder to blood in the urine, and in the uterus to vaginal bleeding.<!--<ref name=Card10/> --> Although localized pain may occur in advanced cancer, the initial swelling is usually painless.<!--<ref name=Card10/> --> Some cancers can cause build up of fluid within the chest or abdomen.<ref name=Card10/>
-===Systemic symptoms===
-General symptoms occur due to distant effects of the cancer that are not related to direct or metastatic spread. These may include: unintentional weight loss, [[fever]], being excessively tired, and changes to the skin.<ref>{{cite book|last=O'Dell|first=edited by Michael D. Stubblefield, Michael W.|title=Cancer rehabilitation principles and practice|year=2009|publisher=Demos Medical|location=New York|isbn=978-1-933864-33-4|page=983|url=http://books.google.ca/books?id=_JaPlNYgXkEC&pg=PT983}}</ref> [[Hodgkin disease]], [[leukemia]]s, and cancers of the liver or kidney can cause a persistent [[fever of unknown origin]].<ref name=Card10/>
-Specific constellations of systemic symptoms, termed [[paraneoplastic phenomenon|paraneoplastic phenomena]], may occur with some cancers. Examples include the appearance of [[myasthenia gravis]] in [[thymoma]] and [[nail clubbing|clubbing]] in [[lung cancer]].<ref name=Card10/>
-===Metastasis===
-{{main|Metastasis}}
-[[Symptoms of metastasis]] are due to the spread of cancer to other locations in the body. They can include enlarged [[lymph node]]s (which can be felt or sometimes seen under the skin and are typically hard), [[hepatomegaly]] (enlarged liver) or [[splenomegaly]] (enlarged spleen) which can be felt in the [[abdomen]], pain or [[fracture]] of affected bones, and [[neurology|neurological]] symptoms.<ref name=Card10/>
-==Causes==
-Cancers are primarily an environmental disease with 90–95% of cases attributed to environmental factors and 5–10% due to genetics.<ref name=Enviro2008/> [[Environment (biophysical)|''Environmental'']], as used by cancer researchers, means any cause that is not [[Heredity|inherited genetically]], not merely pollution.<ref name="isbn0-387-78192-7">{{cite book | author = Kravchenko J, Akushevich I, Manton, KG | title = Cancer mortality and morbidity patterns in the U. S. population: an interdisciplinary approach | publisher = Springer | location = Berlin | year = 2009 | pages = | isbn = 0-387-78192-7 | quote = The term ''environment'' refers not only to air, water, and soil but also to substances and conditions at home and at the workplace, including diet, smoking, alcohol, drugs, exposure to chemicals, sunlight, ionizing radiation, electromagnetic fields, infectious agents, etc. Lifestyle, economic and behavioral factors are all aspects of our environment. }}</ref> Common environmental factors that contribute to cancer death include [[tobacco]] (25–30%), diet and [[obesity]] (30–35%), [[infections]] (15–20%), [[radiation]] (both ionizing and non-ionizing, up to 10%), stress, lack of [[physical activity]], and [[environmental pollutants]].<ref name=Enviro2008/>
-It is nearly impossible to prove what caused a cancer in any individual, because most cancers have multiple possible causes. For example, if a person who uses tobacco heavily develops lung cancer, then it was probably caused by the tobacco use, but since everyone has a small chance of developing lung cancer as a result of air pollution or radiation, then there is a small chance that the cancer developed because of air pollution or radiation.
-===Chemicals===
-{{Further|Alcohol and cancer|Smoking and cancer}}
-[[Image:Cancer smoking lung cancer correlation from NIH.svg|thumb|right|The incidence of [[lung cancer]] is highly correlated with [[smoking]].]]
-Cancer pathogenesis is traceable back to [[DNA mutations]] that impact cell growth and metastasis. Substances that cause DNA mutations are known as mutagens, and mutagens that cause cancers are known as carcinogens. Particular substances have been linked to specific types of cancer. [[Tobacco smoking]] is associated with many forms of cancer,<ref name=Sasco>{{cite journal | author = Sasco AJ, Secretan MB, Straif K | title = Tobacco smoking and cancer: a brief review of recent epidemiological evidence | journal = Lung Cancer | volume = 45 Suppl 2 | issue = | pages = S3–9 | year = 2004 | month = August | pmid = 15552776 | doi = 10.1016/j.lungcan.2004.07.998 }}</ref> and causes 90% of [[lung cancer]].<ref name="pmid9594919">{{cite journal | author = Biesalski HK, Bueno de Mesquita B, Chesson A, Chytil F, Grimble R, Hermus RJ, Köhrle J, Lotan R, Norpoth K, Pastorino U, Thurnham D | title = European Consensus Statement on Lung Cancer: risk factors and prevention. Lung Cancer Panel | journal = CA Cancer J Clin | volume = 48 | issue = 3 | pages = 167–76; discussion 164–6 | year = 1998 | pmid = 9594919 | doi = 10.3322/canjclin.48.3.167 }}</ref>
-Many [[mutagen]]s are also [[carcinogen]]s, but some carcinogens are not mutagens. [[Alcohol]] is an example of a chemical carcinogen that is not a mutagen.<ref name="pmid9751943">{{cite journal | author = Seitz HK, Pöschl G, Simanowski UA | title = Alcohol and cancer | journal = Recent Dev Alcohol | volume = 14 | issue = | pages = 67–95 | year = 1998 | pmid = 9751943 | doi = }}</ref> In Western Europe 10% of cancers in males and 3% of cancers in females are attributed to alcohol.<ref name="pmid21474525">{{cite journal | author = Schütze M, Boeing H, Pischon T, Rehm J, Kehoe T, Gmel G, Olsen A, Tjønneland AM, Dahm CC, Overvad K, Clavel-Chapelon F, Boutron-Ruault MC, Trichopoulou A, Benetou V, Zylis D, Kaaks R, Rohrmann S, Palli D, Berrino F, Tumino R, Vineis P, Rodríguez L, Agudo A, Sánchez MJ, Dorronsoro M, Chirlaque MD, Barricarte A, Peeters PH, van Gils CH, Khaw KT, Wareham N, Allen NE, Key TJ, Boffetta P, Slimani N, Jenab M, Romaguera D, Wark PA, Riboli E, Bergmann MM | title = Alcohol attributable burden of incidence of cancer in eight European countries based on results from prospective cohort study | journal = BMJ | volume = 342 | issue = | pages = d1584 | year = 2011 | pmid = 21474525 | pmc = 3072472 | doi = 10.1136/bmj.d1584 }}</ref>
-Decades of research has demonstrated the link between [[tobacco]] use and cancer in the [[lung cancer|lung]], [[larynx]], head, neck, stomach, bladder, kidney, [[esophagus]] and [[pancreas]].<ref name="pmid12270001">{{cite journal | author = Kuper H, Boffetta P, Adami HO | title = Tobacco use and cancer causation: association by tumour type | journal = J. Intern. Med. | volume = 252 | issue = 3 | pages = 206–24 | year = 2002 | month = September | pmid = 12270001 | doi = 10.1046/j.1365-2796.2002.01022.x }}</ref> Tobacco smoke contains over fifty known carcinogens, including [[nitrosamine]]s and [[polycyclic aromatic hydrocarbon]]s.<ref name=Kuper/> Tobacco is responsible for about one in three of all cancer deaths in the developed world,<ref name=Sasco/> and about one in five worldwide.<ref name=Kuper>{{cite journal | author = Kuper H, Adami HO, Boffetta P | title = Tobacco use, cancer causation and public health impact | journal = J. Intern. Med. | volume = 251 | issue = 6 | pages = 455–66 | year = 2002 | month = June | pmid = 12028500 | doi = 10.1046/j.1365-2796.2002.00993.x }}</ref> [[Lung cancer]] death rates in the United States have mirrored [[tobacco smoking|smoking]] patterns, with increases in smoking followed by dramatic increases in lung cancer death rates and, more recently, decreases in smoking rates since the 1950s followed by decreases in lung cancer death rates in men since 1990.<ref name="pmid16998161">{{cite journal | author = Thun MJ, Jemal A | title = How much of the decrease in cancer death rates in the United States is attributable to reductions in tobacco smoking? | journal = Tob Control | volume = 15 | issue = 5 | pages = 345–7 | year = 2006 | month = October | pmid = 16998161 | pmc = 2563648 | doi = 10.1136/tc.2006.017749 }}</ref><ref name="pmid18434333">{{cite journal | author = Dubey S, Powell CA | title = Update in lung cancer 2007 | journal = Am. J. Respir. Crit. Care Med. | volume = 177 | issue = 9 | pages = 941–6 | year = 2008 | month = May | pmid = 18434333 | pmc = 2720127 | doi = 10.1164/rccm.200801-107UP }}</ref> However, the numbers of smokers worldwide is still rising, leading to what some organizations have described as the ''tobacco epidemic''.<ref name="pmid15217537">{{cite journal | author = Proctor RN | title = The global smoking epidemic: a history and status report | journal = Clin Lung Cancer | volume = 5 | issue = 6 | pages = 371–6 | year = 2004 | month = May | pmid = 15217537 | doi = 10.3816/CLC.2004.n.016 }}</ref>
-Cancer related to one's occupation is believed to represent between 2–20% of all cases.<ref name="pmid18055160">{{cite journal | author = Irigaray P, Newby JA, Clapp R, Hardell L, Howard V, Montagnier L, Epstein S, Belpomme D | title = Lifestyle-related factors and environmental agents causing cancer: an overview | journal = Biomed. Pharmacother. | volume = 61 | issue = 10 | pages = 640–58 | year = 2007 | month = December | pmid = 18055160 | doi = 10.1016/j.biopha.2007.10.006 }}</ref> Every year, at least 200,000 people die worldwide from cancer related to their workplace.<ref name=WHO_occup>{{cite press release |title=WHO calls for prevention of cancer through healthy workplaces |publisher=World Health Organization |date=27 April 2007 |url=http://www.who.int/mediacentre/news/notes/2007/np19/en/index.html |accessdate=13 October 2007}}</ref> Most cancer deaths caused by occupational risk factors occur in the developed world.<ref name=WHO_occup/> It is estimated that approximately 20,000 cancer deaths and 40,000 new cases of cancer each year in the U.S. are attributable to occupation.<ref>{{cite web|url=http://www.cdc.gov/niosh/topics/cancer/|title=National Institute for Occupational Safety and Health- Occupational Cancer |accessdate=13 October 2007|publisher=United States National Institute for Occupational Safety and Health}}</ref> Millions of workers run the risk of developing cancers such as [[lung cancer]] and [[mesothelioma]] from inhaling [[asbestos]] fibers and tobacco smoke, or [[leukemia]] from exposure to [[benzene]] at their workplaces.<ref name=WHO_occup/>
-===Diet and exercise===
-Diet, [[Physical activity|physical inactivity]], and [[obesity]] are related to approximately 30–35% of cancer deaths.<ref name=Enviro2008/><ref name=Nutri06/> In the United States excess body weight is associated with the development of many types of cancer and is a factor in 14–20% of all cancer deaths.<ref name=Nutri06/> Physical inactivity is believed to contribute to cancer risk not only through its effect on body weight but also through negative effects on [[immune system]] and [[endocrine system]].<ref name=Nutri06/>  More than half of the effect from diet is due to [[overnutrition]] rather than from eating too few healthful foods.
-Diets that are very low in vegetables, fruits and whole grains, and high in [[processed meat|processed]] or red meats are linked with a number of cancers.<ref name=Nutri06>{{cite journal | author = Kushi LH, Byers T, Doyle C, Bandera EV, McCullough M, McTiernan A, Gansler T, Andrews KS, Thun MJ | title = American Cancer Society Guidelines on Nutrition and Physical Activity for cancer prevention: reducing the risk of cancer with healthy food choices and physical activity | journal = CA Cancer J Clin | volume = 56 | issue = 5 | pages = 254–81; quiz 313–4 | year = 2006 | pmid = 17005596 | doi = 10.3322/canjclin.56.5.254 }}</ref> A high-[[salt]] diet is linked to [[gastric cancer]], [[aflatoxin B1]], a frequent food contaminate, with liver cancer, and [[Betel nut]] chewing with oral cancer.<ref name="pmid18990005">{{cite journal | author = Park S, Bae J, Nam BH, Yoo KY | title = Aetiology of cancer in Asia | journal = Asian Pac. J. Cancer Prev. | volume = 9 | issue = 3 | pages = 371–80 | year = 2008 | pmid = 18990005 | doi = | url = http://www.apocpcontrol.org/page/popup_paper_file_view.php?pno=MzcxIFBhcmsucCZrY29kZT04MjI=&pgubun=i | format = PDF }}</ref> This may partly explain differences in cancer incidence in different countries.  For example, [[gastric cancer]] is more common in Japan due to its high-salt diet<ref name="pmid19107449">{{cite journal | author = Brenner H, Rothenbacher D, Arndt V | title = Epidemiology of stomach cancer | journal = Methods Mol. Biol. | volume = 472 | issue = | pages = 467–77 | year = 2009 | pmid = 19107449 | doi = 10.1007/978-1-60327-492-0_23 }}</ref> and [[Colorectal cancer|colon cancer]] is more common in the United States. Immigrants develop the risk of their new country, often within one generation, suggesting a substantial link between diet and cancer.<ref name="pmid14278899">{{cite journal | author = Buell P, Dunn JE | title = Cancer mortality among Japanese Issei and Nisei of California | journal = Cancer | volume = 18 | issue = 5 | pages = 656–64 | year = 1965 | month = May | pmid = 14278899 | doi = 10.1002/1097-0142(196505)18:5<656::AID-CNCR2820180515>3.0.CO;2-3 }}</ref>
-===Infection===
-{{Main|Infectious causes of cancer}}
-Worldwide approximately 18% of cancer deaths are related to [[infectious diseases]].<ref name=Enviro2008/> This proportion varies in different regions of the world from a high of 25% in Africa to less than 10% in the developed world.<ref name=Enviro2008/> [[Virus]]es are the usual infectious agents that cause cancer but [[bacteria]] and [[parasites]] may also have an effect.
-A virus that can cause cancer is called an ''[[oncovirus]]''. These include [[human papillomavirus]] ([[cervical carcinoma]]), [[Epstein-Barr virus]] ([[B-cell lymphoproliferative disease]] and [[nasopharyngeal carcinoma]]), [[Kaposi's sarcoma herpesvirus]] ([[Kaposi's Sarcoma]] and primary effusion lymphomas), [[hepatitis B]] and [[hepatitis C]] viruses ([[hepatocellular carcinoma]]), and [[Human T-cell leukemia virus-1]] (T-cell leukemias). Bacterial infection may also increase the risk of cancer, as seen in [[Helicobacter pylori]]-induced [[gastric carcinoma]].<ref name=Viral04>{{cite journal | author = Pagano JS, Blaser M, Buendia MA, Damania B, Khalili K, Raab-Traub N, Roizman B | title = Infectious agents and cancer: criteria for a causal relation | journal = Semin. Cancer Biol. | volume = 14 | issue = 6 | pages = 453–71 | year = 2004 | month = December | pmid = 15489139 | doi = 10.1016/j.semcancer.2004.06.009 }}</ref> Parasitic infections strongly associated with cancer include ''[[Schistosoma haematobium]]'' ([[Bladder cancer|squamous cell carcinoma of the bladder]]) and the [[liver fluke]]s, ''[[Opisthorchis viverrini]]'' and ''[[Clonorchis sinensis]]'' ([[cholangiocarcinoma]]).<ref name="pmid20539059">{{cite journal | author = Samaras V, Rafailidis PI, Mourtzoukou EG, Peppas G, Falagas ME | title = Chronic bacterial and parasitic infections and cancer: a review | journal = J Infect Dev Ctries | volume = 4 | issue = 5 | pages = 267–81 | year = 2010 | month = May | pmid = 20539059 | doi = | url = http://www.jidc.org/index.php/journal/article/download/20539059/387 | format = PDF }}</ref>
-===Radiation===
-{{main|radiation-induced cancer}}
-Up to 10% of invasive cancers are related to radiation exposure, including both [[ionizing radiation]] and [[non-ionizing radiation|non-ionizing]] [[ultraviolet radiation]] .<ref name=Enviro2008/> Additionally, the vast majority of non-invasive cancers are non-melanoma skin cancers caused by non-ionizing [[ultraviolet radiation]].
-Sources of ionizing radiation include [[medical imaging]], and [[radon]] gas. Radiation can cause cancer in most parts of the body, in all animals, and at any age, although radiation-induced solid tumors usually take 10–15 years, and can take up to 40 years, to become clinically manifest, and radiation-induced [[leukemia]]s typically require 2–10 years to appear.<ref name=Little /> Some people, such as those with [[nevoid basal cell carcinoma syndrome]] or [[retinoblastoma]], are more susceptible than average to developing cancer from radiation exposure.<ref name=Little /> Children and adolescents are twice as likely to develop radiation-induced leukemia as adults; radiation exposure before birth has ten times the effect.<ref name=Little /> Ionizing radiation is not a particularly strong mutagen.<ref name=Little /> Residential exposure to radon gas, for example, has similar cancer risks as [[passive smoking]].<ref name=Little /> Low-dose exposures, such as living near a [[nuclear power plant]], are generally believed to have no or very little effect on cancer development.<ref name=Little /> Radiation is a more potent source of cancer when it is combined with other cancer-causing agents, such as radon gas exposure plus smoking tobacco.<ref name=Little />
-Unlike chemical or physical triggers for cancer, ionizing radiation hits molecules within cells randomly. If it happens to strike a [[chromosome]], it can break the chromosome, result in an [[aneuploidy|abnormal number of chromosomes]], inactivate one or more genes in the part of the chromosome that it hit, delete parts of the DNA sequence, cause [[chromosome translocation]]s, or cause other types of [[chromosome abnormalities]].<ref name=Little /> Major damage normally results in the cell dying, but smaller damage may leave a stable, partly functional cell that may be capable of proliferating and developing into cancer, especially if [[tumor suppressor gene]]s were damaged by the radiation.<ref name=Little>{{cite book | editor = Kufe DW, Pollock RE, Weichselbaum RR, Bast RC Jr, Gansler TS, Holland JF, Frei E III | title = Cancer medicine | author = Little JB | chapter = Chapter 14: Ionizing Radiation | edition = 6th | publisher = B.C. Decker | location = Hamilton, Ont | year = 2000 | isbn = 1-55009-113-1 | url = http://www.ncbi.nlm.nih.gov/books/NBK20793/ }}</ref> Three independent stages appear to be involved in the creation of cancer with ionizing radiation: morphological changes to the cell, acquiring [[cellular immortality]] (losing normal, life-limiting cell regulatory processes), and adaptations that favor formation of a tumor.<ref name=Little /> Even if the radiation particle does not strike the DNA directly, it triggers responses from cells that indirectly increase the likelihood of mutations.<ref name=Little />
-Medical use of ionizing radiation is a growing source of radiation-induced cancers. Ionizing radiation may be used to treat other cancers, but this may, in some cases, induce a second form of cancer.<ref name=Little /> It is also used in some kinds of [[medical imaging]]. One report estimates that approximately 29,000 future cancers could be related to the approximately 70 million [[CT scan]]s performed in the US in 2007.<ref name="pmid20008689">{{cite journal | author = Berrington de González A, Mahesh M, Kim KP, Bhargavan M, Lewis R, Mettler F, Land C | title = Projected cancer risks from computed tomographic scans performed in the United States in 2007 | journal = Arch. Intern. Med. | volume = 169 | issue = 22 | pages = 2071–7 | year = 2009 | month = December | pmid = 20008689 | doi = 10.1001/archinternmed.2009.440 }}</ref> It is estimated that 0.4% of cancers in 2007 in the United States are due to CTs performed in the past and that this may increase to as high as 1.5–2% with rates of CT usage during this same time period.<ref name="pmid18046031">{{cite journal | author = Brenner DJ, Hall EJ | title = Computed tomography—an increasing source of radiation exposure | journal = N. Engl. J. Med. | volume = 357 | issue = 22 | pages = 2277–84 | year = 2007 | month = November | pmid = 18046031 | doi = 10.1056/NEJMra072149 }}</ref>
-Prolonged exposure to [[ultraviolet radiation]] from the [[sun]] can lead to [[melanoma]] and other skin malignancies.<ref name=Cleaver>{{cite book | author = Cleaver JE, Mitchell DL | editor = Bast RC, Kufe DW, Pollock RE, ''et al.''| title = Holland-Frei Cancer Medicine | edition = 5th | publisher = B.C. Decker | location = Hamilton, Ontario | year = 2000 | chapter = 15. Ultraviolet Radiation Carcinogenesis | isbn = 1-55009-113-1 | oclc = | url = http://www.ncbi.nlm.nih.gov/books/NBK20854/ | accessdate= 31 January 2011 }}</ref> Clear evidence establishes ultraviolet radiation, especially the non-ionizing medium wave [[UVB]], as the cause of most non-melanoma [[skin cancer]]s, which are the most common forms of cancer in the world.<ref name=Cleaver />
-Non-ionizing [[radio frequency]] radiation from [[mobile phone]]s, [[electric power transmission]], and other similar sources have been described as a [[possible carcinogen]] by the [[World Health Organization]]'s [[International Agency for Research on Cancer]].<ref>{{cite web|title=IARC classifies radiofrequency electromagnetic fields as possibly carcinogenic to humans |url=http://www.iarc.fr/en/media-centre/pr/2011/pdfs/pr208_E.pdf|work=World Health Organization}}</ref>
-===Heredity===
-{{Main|Cancer syndrome}}
-The vast majority of cancers are non-hereditary ("sporadic cancers"). [[Hereditary cancer]]s are primarily caused by an inherited genetic defect. Less than 0.3% of the population are carriers of a genetic mutation which has a large effect on cancer risk and these cause less than 3–10% of all cancer.<ref name=Expert09>{{cite journal | author = Roukos DH | title = Genome-wide association studies: how predictable is a person's cancer risk? | journal = Expert Rev Anticancer Ther | volume = 9 | issue = 4 | pages = 389–92 | year = 2009 | month = April | pmid = 19374592 | doi = 10.1586/era.09.12 }}</ref> Some of these [[syndrome]]s include: certain inherited mutations in the genes ''[[BRCA1]]'' and ''[[BRCA2]]'' with a more than 75% risk of [[breast cancer]] and [[ovarian cancer]],<ref name=Expert09/> and [[hereditary nonpolyposis colorectal cancer]] (HNPCC or Lynch syndrome) which is present in about 3% of people with [[colorectal cancer]],<ref name=Lancet10>{{cite journal | author = Cunningham D, Atkin W, Lenz HJ, Lynch HT, Minsky B, Nordlinger B, Starling N | title = Colorectal cancer | journal = Lancet | volume = 375 | issue = 9719 | pages = 1030–47 | year = 2010 | month = March | pmid = 20304247 | doi = 10.1016/S0140-6736(10)60353-4 }}</ref> among others.
-===Physical agents===
-Some substances cause cancer primarily through their physical, rather than chemical, effects on cells.<ref name=Maltoni>{{cite book | author = Maltoni CFM, Holland JF | editor = Bast RC, Kufe DW, Pollock RE, ''et al.'' | title = Holland-Frei Cancer Medicine | edition = 5th | publisher = B.C. Decker | location = Hamilton, Ontario | year = 2000 | chapter = Chapter 16: Physical Carcinogens | isbn = 1-55009-113-1 | url = http://www.ncbi.nlm.nih.gov/books/NBK20770/ | accessdate = 31 January 2011}}</ref>
-A prominent example of this is prolonged exposure to [[asbestos]], naturally occurring mineral fibers which are a major cause of [[mesothelioma]], a type of cancer of the [[serous membrane]].<ref name=Maltoni /> Other substances in this category, including both naturally occurring and synthetic asbestos-like fibers such as [[wollastonite]], [[attapulgite]], [[glass wool]], and [[rock wool]], are believed to have similar effects.<ref name=Maltoni />
-Nonfibrous particulate materials that cause cancer include powdered metallic [[cobalt]] and [[nickel]], and [[crystalline silica]] ([[quartz]], [[cristobalite]], and [[tridymite]]).<ref name=Maltoni />
-Usually, physical carcinogens must get inside the body (such as through inhaling tiny pieces) and require years of exposure to develop cancer.<ref name=Maltoni />
-Physical trauma resulting in cancer is relatively rare.<ref name=Gaeta>{{cite book|author=Gaeta, John F|editor=Bast RC, Kufe DW, Pollock RE, ''et al.''|title=Holland-Frei Cancer Medicine|edition=5th|publisher=B.C. Decker|location=Hamilton, Ontario|year=2000|chapter=Chapter 17: Trauma and Inflammation|isbn=1-55009-113-1|oclc=|url=http://www.ncbi.nlm.nih.gov/books/NBK20784/|accessdate=27 January 2011}}</ref> Claims that breaking bone resulted in bone cancer, for example, have never been proven.<ref name=Gaeta /> Similarly, physical trauma is not accepted as a cause for cervical cancer, breast cancer, or brain cancer.<ref name=Gaeta />
-One accepted source is frequent, long-term application of hot objects to the body. It is possible that repeated burns on the same part of the body, such as those produced by [[kanger]] and kairo heaters (charcoal [[hand warmer]]s), may produce skin cancer, especially if carcinogenic chemicals are also present.<ref name=Gaeta /> Frequently drinking scalding hot tea may produce esophageal cancer.<ref name=Gaeta />
-Generally, it is believed that the cancer arises, or a pre-existing cancer is encouraged, during the process of repairing the trauma, rather than the cancer being caused directly by the trauma.<ref name=Gaeta /> However, repeated injuries to the same tissues might promote excessive cell proliferation, which could then increase the odds of a cancerous mutation. There is no evidence that [[inflammation]] itself causes cancer.<ref name=Gaeta />
-===Hormones===
-Some [[hormone]]s play a role in the development of cancer by promoting [[cell proliferation]].<ref name=Henderson>{{cite book | author = Henderson BE, Bernstein L, Ross
-RK | editor = Bast RC, Kufe DW, Pollock RE, ''et al.''
-|title=Holland-Frei Cancer Medicine
-|edition=5th
-|publisher=B.C. Decker
-|location=Hamilton, Ontario
-|year=2000
-|chapter=Chapter 13: Hormones and the Etiology of Cancer
-|isbn=1-55009-113-1
-|oclc=
-|url=http://www.ncbi.nlm.nih.gov/books/NBK20759/
-|accessdate=27 January 2011}}</ref> Hormones are important agents in sex-related cancers such as cancer of the breast, [[endometrium]], prostate, ovary, and [[testis]], and also of [[thyroid cancer]] and [[bone cancer]].<ref name=Henderson />
-An individual's hormone levels are mostly determined genetically, so this may at least partly explains the presence of some cancers that run in families that do not seem to have any cancer-causing genes.<ref name=Henderson /> For example, the daughters of women who have breast cancer have significantly higher levels of [[estrogen]] and [[progesterone]] than the daughters of women without breast cancer. These higher hormone levels may explain why these women have higher risk of breast cancer, even in the absence of a breast-cancer gene.<ref name=Henderson /> Similarly, men of African ancestry have significantly higher levels of testosterone than men of European ancestry, and have a correspondingly much higher level of prostate cancer.<ref name=Henderson /> Men of Asian ancestry, with the lowest levels of testosterone-activating [[androstanediol glucuronide]], have the lowest levels of prostate cancer.<ref name=Henderson />
-However, non-genetic factors are also relevant: obese people have higher levels of some hormones associated with cancer and a higher rate of those cancers.<ref name=Henderson /> Women who take [[Hormone replacement therapy (menopause)|hormone replacement therapy]] have a higher risk of developing cancers associated with those hormones.<ref name=Henderson /> On the other hand, people who exercise far more than average have lower levels of these hormones, and lower risk of cancer.<ref name=Henderson /> [[Osteosarcoma]] may be promoted by [[growth hormone]]s.<ref name=Henderson /> Some treatments and prevention approaches leverage this cause by artificially reducing hormone levels, and thus discouraging hormone-sensitive cancers.<ref name=Henderson />
-===Other===
-Excepting the rare transmissions that occur with pregnancies and only a marginal few organ donors, cancer is generally not a [[transmission (medicine)|transmissible disease]]. The main reason for this is tissue graft rejection caused by [[major histocompatibility complex|MHC]] [[histocompatibility|incompatibility]].<ref name=Tolar>{{cite journal | author = Tolar J, Neglia JP | title = Transplacental and other routes of cancer transmission between individuals | journal = J. Pediatr. Hematol. Oncol. | volume = 25 | issue = 6 | pages = 430–4 | year = 2003 | month = June | pmid = 12794519 | doi = 10.1097/00043426-200306000-00002 }}</ref> In humans and other vertebrates, the immune system uses MHC antigens to differentiate between "self" and "non-self" cells because these antigens are different from person to person. When non-self antigens are encountered, the immune system reacts against the appropriate cell. Such reactions may protect against tumour cell engraftment by eliminating implanted cells. In the United States, approximately 3,500 pregnant women have a malignancy annually, and transplacental transmission of [[acute leukaemia]], [[lymphoma]], [[melanoma]] and [[carcinoma]] from mother to fetus has been observed.<ref name=Tolar/> The development of donor-derived tumors from organ transplants is exceedingly rare. The main cause of organ transplant associated tumors seems to be malignant melanoma, that was undetected at the time of organ harvest.<ref name="pmid16957717">{{cite journal | author = Dingli D, Nowak MA | title = Cancer biology: infectious tumour cells | journal = Nature | volume = 443 | issue = 7107 | pages = 35–6 | year = 2006 | month = September | pmid = 16957717 | pmc = 2711443 | doi = 10.1038/443035a | bibcode = 2006Natur.443...35D }}</ref> Job stress does not appear to be a significant factor at least in lung, colorectal, breast and prostate cancers.<ref>{{cite journal|last=Heikkilä|first=K|coauthors=Nyberg, ST; Theorell, T; Fransson, EI; Alfredsson, L; Bjorner, JB; Bonenfant, S; Borritz, M; Bouillon, K; Burr, H; Dragano, N; Geuskens, GA; Goldberg, M; Hamer, M; Hooftman, WE; Houtman, IL; Joensuu, M; Knutsson, A; Koskenvuo, M; Koskinen, A; Kouvonen, A; Madsen, IE; Magnusson Hanson, LL; Marmot, MG; Nielsen, ML; Nordin, M; Oksanen, T; Pentti, J; Salo, P; Rugulies, R; Steptoe, A; Suominen, S; Vahtera, J; Virtanen, M; Väänänen, A; Westerholm, P; Westerlund, H; Zins, M; Ferrie, JE; Singh-Manoux, A; Batty, GD; Kivimäki, M; IPD-Work, Consortium|title=Work stress and risk of cancer: meta-analysis of 5700 incident cancer events in 116 000 European men and women.|journal=BMJ (Clinical research ed.)|date=2013 Feb 7|volume=346|pages=f165|pmid=23393080}}</ref>
-==Pathophysiology==
-{{Main|Carcinogenesis}}
-[[File:Cancer requires multiple mutations from NIHen.png|thumb|right|Cancers are caused by a series of mutations. Each mutation alters the behavior of the cell somewhat.]]
-Cancer is fundamentally a disease of failure of regulation of tissue growth. In order for a normal cell to [[malignant transformation|transform]] into a cancer cell, the [[genes]] which regulate cell growth and differentiation must be altered.<ref name="pmid18234754">{{cite journal | author = Croce CM | title = Oncogenes and cancer | journal = N. Engl. J. Med. | volume = 358 | issue = 5 | pages = 502–11 | year = 2008 | month = January | pmid = 18234754 | doi = 10.1056/NEJMra072367 }}</ref>
-The affected genes are divided into two broad categories. [[Oncogene]]s are genes which promote cell growth and reproduction. [[Tumor suppressor gene]]s are genes which inhibit cell division and survival. Malignant transformation can occur through the formation of novel oncogenes, the inappropriate over-expression of normal oncogenes, or by the under-expression or disabling of tumor suppressor genes. Typically, changes in ''many'' genes are required to transform a normal cell into a cancer cell.<ref name="pmid11905807">{{cite journal | author = Knudson AG | title = Two genetic hits (more or less) to cancer | journal = Nat. Rev. Cancer | volume = 1 | issue = 2 | pages = 157–62 | year = 2001 | month = November | pmid = 11905807 | doi = 10.1038/35101031 }}</ref>
-Genetic changes can occur at different levels and by different mechanisms. The gain or loss of an entire [[chromosome]] can occur through errors in [[mitosis]]. More common are [[mutation]]s, which are changes in the [[nucleotide]] sequence of genomic DNA.
-Large-scale mutations involve the deletion or gain of a portion of a chromosome. [[Gene duplication|Genomic amplification]] occurs when a cell gains many copies (often 20 or more) of a small chromosomal locus, usually containing one or more oncogenes and adjacent genetic material. [[Chromosomal translocation|Translocation]] occurs when two separate chromosomal regions become abnormally fused, often at a characteristic location. A well-known example of this is the [[Philadelphia chromosome]], or translocation of chromosomes 9 and 22, which occurs in [[chronic myelogenous leukemia]], and results in production of the [[BCR gene|BCR]]-[[abl gene|abl]] [[fusion protein]], an oncogenic [[tyrosine kinase]].
-Small-scale mutations include point mutations, deletions, and insertions, which may occur in the [[Promoter (biology)|promoter]] region of a gene and affect its [[gene expression|expression]], or may occur in the gene's [[coding sequence]] and alter the function or stability of its [[protein]] product. Disruption of a single gene may also result from [[provirus|integration of genomic material]] from a [[DNA virus]] or [[retrovirus]], and resulting in the expression of ''viral'' oncogenes in the affected cell and its descendants.
-Replication of the enormous amount of data contained within the DNA of living cells will [[probability|probabilistically]] result in some errors (mutations). Complex error correction and prevention is built into the process, and safeguards the cell against cancer. If significant error occurs, the damaged cell can "self-destruct" through programmed cell death, termed [[apoptosis]]. If the error control processes fail, then the mutations will survive and be passed along to [[cell division|daughter cells]].
-Some environments make errors more likely to arise and propagate. Such environments can include the presence of disruptive substances called [[carcinogens]], repeated physical injury, heat, ionising radiation, or [[hypoxia (medical)|hypoxia]]<ref>{{cite journal | author = Nelson DA, Tan TT, Rabson AB, Anderson D, Degenhardt K, White E | title = Hypoxia and defective apoptosis drive genomic instability and tumorigenesis | journal = Genes & Development | volume = 18 | issue = 17 | pages = 2095–107 | year = 2004 | month = September | pmid = 15314031 | pmc = 515288 | doi = 10.1101/gad.1204904 }}</ref>
-The errors which cause cancer are ''self-amplifying'' and ''compounding'', for example:
-* A mutation in the error-correcting machinery of a cell might cause that cell and its children to accumulate errors more rapidly.
-* A further mutation in an oncogene might cause the cell to reproduce more rapidly and more frequently than its normal counterparts.
-* A further mutation may cause loss of a tumour suppressor gene, disrupting the apoptosis signalling pathway and resulting in the cell becoming immortal.
-* A further mutation in signaling machinery of the cell might send error-causing signals to nearby cells.
-The transformation of normal cell into cancer is akin to a [[chain reaction]] caused by initial errors, which compound into more severe errors, each progressively allowing the cell to escape the controls that limit normal tissue growth. This rebellion-like scenario becomes an undesirable [[survival of the fittest]], where the driving forces of [[evolution]] work against the body's design and enforcement of order. Once cancer has begun to develop, this ongoing process, termed ''clonal evolution'' drives progression towards more invasive stages.<ref name="pmid17109012">{{cite journal | author = Merlo LM, Pepper JW, Reid BJ, Maley CC | title = Cancer as an evolutionary and ecological process | journal = Nat. Rev. Cancer | volume = 6 | issue = 12 | pages = 924–35 | year = 2006 | month = December | pmid = 17109012 | doi = 10.1038/nrc2013 }}</ref>
-==Diagnosis==
-[[Image:Thorax pa peripheres Bronchialcarcinom li OF markiert.jpg|thumb|Chest x-ray showing lung cancer in the left lung.]]
-Most cancers are initially recognized either because of the appearance of signs or symptoms or through [[cancer screening|screening]]. Neither of these lead to a definitive diagnosis, which requires the examination of a tissue sample by a [[anatomical pathology|pathologist]]. People with suspected cancer are investigated with [[medical test]]s. These commonly include [[blood test]]s, [[X-ray]]s, [[X-ray computed tomography|CT scans]] and [[endoscopy]].
-===Classification===
-{{further2|[[List of cancer types]]|[[List of oncology-related terms]]}}
-Cancers are classified by the [[List of distinct cell types in the adult human body|type of cell]] that the tumor cells resemble and is therefore presumed to be the origin of the tumor. These types include:
-* [[Carcinoma]]: Cancers derived from [[epithelium|epithelial]] cells. This group includes many of the most common cancers, particularly in the aged, and include nearly all those developing in the [[breast cancer|breast]], [[prostate cancer|prostate]], [[lung cancer|lung]], [[pancreas]], and [[Colorectal cancer|colon]].
-* [[Sarcoma]]: Cancers arising from [[connective tissue]] (i.e. [[bone]], [[cartilage]], [[fat]], [[nerve]]), each of which develop from cells originating in [[mesenchyme|mesenchymal]] cells outside the bone marrow.
-* [[Lymphoma]] and [[leukemia]]: These two classes of cancer arise from hematopoietic ([[blood]]-forming) cells that leave the marrow and tend to mature in the lymph nodes and blood, respectively. Leukemia is the most common type of [[cancer in children]] accounting for about 30%.<ref>{{cite book |author=Varricchio, Claudette G. |title=A cancer source book for nurses |publisher=Jones and Bartlett Publishers |location=Boston |year=2004 |page=229 |isbn=0-7637-3276-1 |oclc= |url=http://books.google.co.jp/books?id=jkqdgZcF9qcC&pg=PA229}}</ref>
-* [[Germ cell tumor]]: Cancers derived from [[pluripotent]] cells, most often presenting in the [[testicular cancer|testicle]] or the [[ovarian cancer|ovary]] ([[seminoma]] and [[dysgerminoma]], respectively).
-* [[Blastoma]]: Cancers derived from immature "precursor" cells or embryonic tissue. Blastomas are more common in children than in older adults.
-Cancers are usually named using ''-carcinoma'', ''-sarcoma'' or ''-blastoma'' as a suffix, with the Latin or Greek word for the [[organ (anatomy)|organ]] or tissue of origin as the root. For example, cancers of the liver [[parenchyma]] arising from malignant epithelial cells is called ''[[hepatocarcinoma]]'', while a malignancy arising from primitive liver precursor cells is called a [[hepatoblastoma]], and a cancer arising from fat cells is called a ''[[liposarcoma]]''. For some common cancers, the English organ name is used. For example, the most common type of [[breast cancer]] is called ''[[mammary ductal carcinoma|ductal carcinoma of the breast]]''. Here, the adjective ''ductal'' refers to the appearance of the cancer under the microscope, which suggests that it has originated in the milk ducts.
-[[Benign tumor]]s (which are not cancers) are named using ''-oma'' as a suffix with the organ name as the root. For example, a benign tumor of smooth muscle cells is called a ''[[leiomyoma]]'' (the common name of this frequently occurring benign tumor in the uterus is ''[[uterine fibroid|fibroid]]''). Confusingly, some types of cancer use the ''-noma'' suffix, examples including [[melanoma]] and [[seminoma]].
-Some types of cancer are named for the size and shape of the cells under a microscope, such as [[giant cell carcinoma]], [[spindle cell carcinoma]], and [[small cell carcinoma]].
-===Pathology===
-The tissue [[medical diagnosis|diagnosis]] given by the pathologist indicates the type of cell that is proliferating, its [[histological grade]], genetic abnormalities, and other features of the tumor. Together, this information is useful to evaluate the [[prognosis]] of the patient and to choose the best treatment. [[Cytogenetics]] and [[immunohistochemistry]] are other types of testing that the pathologist may perform on the tissue specimen. These tests may provide information about the molecular changes (such as [[mutation]]s, [[fusion gene]]s, and numerical [[chromosome]] changes) that has happened in the cancer cells, and may thus also indicate the future behavior of the cancer (prognosis) and best treatment.
-<gallery>
-Image:Breast cancer gross appearance.jpg|An invasive [[ductal carcinoma]] of the breast (pale area at the center) surrounded by spikes of whitish scar tissue and yellow fatty tissue.
-Image:Colon cancer 2.jpg|An invasive [[colorectal carcinoma]] (top center) in a [[colectomy]] specimen.
-Image:Lung cancer.jpg|A [[squamous cell carcinoma]] (the whitish tumor) near the [[bronchi]] in a lung specimen.
-Image:BreastCancer.jpg|A large invasive [[Mammary ductal carcinoma|ductal carcinoma]] in a [[mastectomy]] specimen.
-</gallery>
-==Prevention==
-Cancer prevention is defined as active measures to decrease the risk of cancer.<ref>{{cite web | url=http://www.mayoclinic.com/health/cancer-prevention/CA00024 | title=Cancer prevention: 7 steps to reduce your risk | publisher=[[Mayo Clinic]] | date=27 September 2008 | accessdate=30 January 2010}}</ref> The vast majority of cancer cases are due to environmental risk factors, and many, but not all, of these environmental factors are controllable lifestyle choices. Thus, cancer is considered a largely preventable disease.<ref name=Danaei>{{cite journal | author = Danaei G, Vander Hoorn S, Lopez AD, Murray CJ, Ezzati M | title = Causes of cancer in the world: comparative risk assessment of nine behavioural and environmental risk factors | journal = Lancet | volume = 366 | issue = 9499 | pages = 1784–93 | year = 2005 | pmid = 16298215 | doi = 10.1016/S0140-6736(05)67725-2 }}</ref> Greater than 30% of cancer deaths could be prevented by avoiding risk factors including: [[tobacco]], [[overweight]] / [[obesity]], an insufficient diet, [[physical inactivity]], [[alcohol]], [[sexually transmitted infection]]s, and [[air pollution]].<ref name="Cancer Cancer">{{cite web |url=http://www.who.int/mediacentre/factsheets/fs297/en/ |title=Cancer |work=World Health Organization |accessdate=9 January 2011}}</ref> Not all environmental causes are controllable, such as naturally occurring [[background radiation]], and other cases of cancer are caused through hereditary genetic disorders, and thus it is not possible to prevent all cases of cancer.
-===Dietary===
-{{Main|Diet and cancer}}
-While many dietary recommendations have been proposed to reduce the risk of cancer, few have significant supporting scientific evidence.<ref name=Diet11>{{cite journal | author = Wicki A, Hagmann, J | title = Diet and cancer. | journal = Swiss medical weekly | volume = 141 | issue = | pages = w13250 | year = 2011 | month = September | pmid = 21904992 | doi = 10.4414/smw.2011.13250 }}</ref> The primary dietary factors that increase risk are [[obesity]] and [[alcohol]] consumption; with a diet low in fruits and vegetables and high in red meat being implicated but not confirmed.<ref name="pmid22202045">{{cite journal | author = Cappellani A, Di Vita M, Zanghi A, Cavallaro A, Piccolo G, Veroux M, Berretta M, Malaguarnera M, Canzonieri V, Lo Menzo E | title = Diet, obesity and breast cancer: an update | journal = Front Biosci (Schol Ed) | volume = 4 | issue = | pages = 90–108 | year = 2012 | pmid = 22202045 | doi = }}</ref><ref name="pmid21119663">{{cite journal | author = Key TJ | title = Fruit and vegetables and cancer risk | journal = Br. J. Cancer | volume = 104 | issue = 1 | pages = 6–11 | year = 2011 | month = January | pmid = 21119663 | pmc = 3039795 | doi = 10.1038/sj.bjc.6606032 }}</ref> Consumption of [[coffee]] is associated with a reduced risk of [[liver cancer]].<ref name="pmid17484871">{{cite journal | author = Larsson SC, Wolk A | title = Coffee consumption and risk of liver cancer: a meta-analysis | journal = Gastroenterology | volume = 132 | issue = 5 | pages = 1740–5 | year = 2007 | month = May | pmid = 17484871 | doi = 10.1053/j.gastro.2007.03.044 }}</ref> Studies have linked consumption of red or processed meat to an increased risk of breast cancer, [[Colorectal cancer|colon cancer]], and [[pancreatic cancer]], a phenomenon which could be due to the presence of carcinogens in meats cooked at high temperatures.<ref name="pmid19838915">{{cite journal | author = Zheng W, Lee SA | title = Well-done meat intake, heterocyclic amine exposure, and cancer risk | journal = Nutr Cancer | volume = 61 | issue = 4 | pages = 437–46 | year = 2009 | pmid = 19838915 | pmc = 2769029 | doi = 10.1080/01635580802710741 }}</ref><ref name="pmid20374790">{{cite journal | author = Ferguson LR | title = Meat and cancer | journal = Meat Sci. | volume = 84 | issue = 2 | pages = 308–13 | year = 2010 | month = February | pmid = 20374790 | doi = 10.1016/j.meatsci.2009.06.032 }}</ref> Dietary recommendations for cancer prevention typically include an emphasis on vegetables, fruit, whole grains,  and fish, and an avoidance of red meat, animal fats and refined carbohydrates.  However, these recommendations are based on relatively limited evidence.<ref name=Diet11/>
-===Medication===
-The concept that medications can be used to prevent cancer is attractive, and evidence supports their use in a few defined circumstances.<ref>Holland Chp.33</ref> In the general population [[NSAIDs]] reduce the risk of [[colorectal cancer]] however due to the cardiovascular and gastrointestinal side effects they cause overall harm when used for prevention.<ref name="pmid17339623">{{cite journal | author = Rostom A, Dubé C, Lewin G, Tsertsvadze A, Barrowman N, Code C, Sampson M, Moher D | title = Nonsteroidal anti-inflammatory drugs and cyclooxygenase-2 inhibitors for primary prevention of colorectal cancer: a systematic review prepared for the U.S. Preventive Services Task Force | journal = Ann. Intern. Med. | volume = 146 | issue = 5 | pages = 376–89 | year = 2007 | month = March | pmid = 17339623 | doi = }}</ref> [[Aspirin]] has been found to reduce the risk of death from cancer by about 7%.<ref name="pmid21144578">{{cite journal | author = Rothwell PM, Fowkes FG, Belch JF, Ogawa H, Warlow CP, Meade TW | title = Effect of daily aspirin on long-term risk of death due to cancer: analysis of individual patient data from randomised trials | journal = Lancet | volume = 377 | issue = 9759 | pages = 31–41 | year = 2011 | month = January | pmid = 21144578 | doi = 10.1016/S0140-6736(10)62110-1 }}</ref> [[COX-2 inhibitor]] may decrease the rate of [[polyp]] formation in people with [[familial adenomatous polyposis]] however are associated with the same adverse effects as NSAIDs.<ref name="pmid20594533">{{cite journal | author = Cooper K, Squires H, Carroll C, Papaioannou D, Booth A, Logan RF, Maguire C, Hind D, Tappenden P | title = Chemoprevention of colorectal cancer: systematic review and economic evaluation | journal = Health Technol Assess | volume = 14 | issue = 32 | pages = 1–206 | year = 2010 | month = June | pmid = 20594533 | doi = 10.3310/hta14320 }}</ref> Daily use of [[tamoxifen]] or [[raloxifene]] has been demonstrated to reduce the risk of developing [[breast cancer]] in high-risk women.<ref name="pmid19020189">{{cite journal | author = Thomsen A, Kolesar JM | title = Chemoprevention of breast cancer | journal = Am J Health Syst Pharm | volume = 65 | issue = 23 | pages = 2221–8 | year = 2008 | month = December | pmid = 19020189 | doi = 10.2146/ajhp070663 }}</ref> The benefit verses harm for [[5-alpha-reductase inhibitor]] such as [[finasteride]] is not clear.<ref name="pmid18425978">{{cite journal | author = Wilt TJ, MacDonald R, Hagerty K, Schellhammer P, Kramer BS | title = Five-alpha-reductase Inhibitors for prostate cancer prevention | journal = Cochrane Database Syst Rev | volume = | issue = 2 | pages = CD007091 | year = 2008 | pmid = 18425978 | doi = 10.1002/14651858.CD007091 }}</ref>
-[[Vitamin]]s have not been found to be effective at preventing cancer,<ref name="pmid20939459">{{cite journal | author = | title = Vitamins and minerals: not for cancer or cardiovascular prevention | journal = Prescrire Int | volume = 19 | issue = 108 | pages = 182 | year = 2010 | month = August | pmid = 20939459 | doi = | url = http://english.prescrire.org/en/81/168/46461/0/2010/ArchiveNewsDetails.aspx?page=2 }}</ref> although low blood levels of [[vitamin D]] are correlated with increased cancer risk.<ref name="pmid16595781">{{cite journal | author = Giovannucci E, Liu Y, Rimm EB, Hollis BW, Fuchs CS, Stampfer MJ, Willett WC | title = Prospective study of predictors of vitamin D status and cancer incidence and mortality in men | journal = J. Natl. Cancer Inst. | volume = 98 | issue = 7 | pages = 451–9 | year = 2006 | month = April | pmid = 16595781 | doi = 10.1093/jnci/djj101 }}</ref><ref>{{cite web|url=http://www.cancer.org/docroot/NWS/content/NWS_1_1x_Vitamin_D_Has_Role_in_Colon_Cancer_Prevention.asp|title=Vitamin D Has Role in Colon Cancer Prevention|accessdate=27 July 2007 | archiveurl = http://web.archive.org/web/20061204052746/http://www.cancer.org/docroot/NWS/content/NWS_1_1x_Vitamin_D_Has_Role_in_Colon_Cancer_Prevention.asp| archivedate = 4 December 2006 }}</ref> Whether this relationship is causal and vitamin D supplementation is protective is not determined.<ref name="pmid16595770">{{cite journal | author = Schwartz GG, Blot WJ | title = Vitamin D status and cancer incidence and mortality: something new under the sun | journal = J. Natl. Cancer Inst. | volume = 98 | issue = 7 | pages = 428–30 | year = 2006 | month = April | pmid = 16595770 | doi = 10.1093/jnci/djj127 }}</ref> [[Beta-carotene]] supplementation has been found to increase [[lung cancer]] rates in those who are high risk.<ref name="pmid21738614">{{cite journal | author = Fritz H, Kennedy D, Fergusson D, Fernandes R, Doucette S, Cooley K, Seely A, Sagar S, Wong R, Seely D | title = Vitamin A and retinoid derivatives for lung cancer: a systematic review and meta analysis | journal = PLoS ONE | volume = 6 | issue = 6 | pages = e21107 | year = 2011 | pmid = 21738614 | pmc = 3124481 | doi = 10.1371/journal.pone.0021107 |bibcode = 2011PLoSO...6E1107F }}</ref> [[Folic acid]] supplementation has not been found effective in preventing colon cancer and may increase colon polyps.<ref name="pmid17551129">{{cite journal | author = Cole BF, Baron JA, Sandler RS, Haile RW, Ahnen DJ, Bresalier RS, McKeown-Eyssen G, Summers RW, Rothstein RI, Burke CA, Snover DC, Church TR, Allen JI, Robertson DJ, Beck GJ, Bond JH, Byers T, Mandel JS, Mott LA, Pearson LH, Barry EL, Rees JR, Marcon N, Saibil F, Ueland PM, Greenberg ER | title = Folic acid for the prevention of colorectal adenomas: a randomized clinical trial | journal = JAMA | volume = 297 | issue = 21 | pages = 2351–9 | year = 2007 | month = June | pmid = 17551129 | doi = 10.1001/jama.297.21.2351 }}</ref>
-===Vaccination===
-[[Vaccine]]s have been developed that prevent some infection by some viruses.<ref name=vacc_facts_nci>{{cite web | url=http://www.cancer.gov/cancertopics/factsheet/cancervaccine | title=Cancer Vaccine Fact Sheet | publisher=[[National Cancer Institute|NCI]] | date=8 June 2006 | accessdate=15 November 2008}}</ref> [[Human papillomavirus vaccine]] ([[Gardasil]] and [[Cervarix]]) decreases the risk of developing [[cervical cancer]].<ref name=vacc_facts_nci/> The [[hepatitis B vaccine]] prevents infection with hepatitis B virus and thus decreases the risk of liver cancer.<ref name=vacc_facts_nci/>
-==Screening==
-{{Main|Cancer screening}}
-Unlike diagnosis efforts prompted by [[symptom]]s and [[medical sign]]s, cancer screening involves efforts to detect cancer after it has formed, but before any noticeable symptoms appear.<ref name=NIH>{{cite web |url=http://www.cancer.gov/cancertopics/pdq/screening/overview/Patient |title=What Is Cancer Screening? |work=National Cancer Institute |accessdate=}}</ref> This may involve [[physical examination]], [[blood test|blood]] or [[urine test]]s, or [[medical imaging]].<ref name=NIH/>
-Cancer screening is currently not possible for many types of cancers, and even when tests are available, they may not be recommended for everyone. ''[[Universal screening]]'' or ''mass screening'' involves screening everyone.<ref name=Wilson>Wilson JMG, Jungner G. (1968) [http://whqlibdoc.who.int/php/WHO_PHP_34.pdf Principles and practice of screening for disease.] Geneva:[[World Health Organization]]. Public Health Papers, #34.</ref> ''Selective screening'' identifies people who are known to be at higher risk of developing cancer, such as people with a family history of cancer.<ref name=Wilson /> Several factors are considered to determine whether the benefits of screening outweigh the risks and the costs of screening.<ref name=NIH/> These factors include:
-* Possible harms from the screening test: for example, X-ray images involve exposure to potentially harmful [[ionizing radiation]].
-* The likelihood of the test correctly identifying cancer.
-* The likelihood of cancer being present: Screening is not normally useful for rare cancers.
-* Possible harms from follow-up procedures.
-* Whether suitable treatment is available.
-* Whether early detection improves treatment outcomes.
-* Whether the cancer will ever need treatment.
-* Whether the test is acceptable to the people: If a screening test is too burdensome (for example, being extremely painful), then people will refuse to participate.<ref name=Wilson />
-* Cost of the test.
-===Recommendations===
-The [[U.S. Preventive Services Task Force]] (USPSTF) strongly recommends [[cervical cancer]] screening in women who are [[sexually active]] and have a [[cervix]] at least until the age of 65.<ref>{{cite web |url=http://www.uspreventiveservicestaskforce.org/uspstf/uspscerv.htm |title=Screening for Cervical Cancer |year=2003 |work=[[U.S. Preventive Services Task Force]]}}</ref> They recommend that Americans be screened for [[colorectal cancer]] via [[fecal occult blood]] testing, [[sigmoidoscopy]], or [[colonoscopy]] starting at age 50 until age 75.<ref>{{cite web |url=http://www.uspreventiveservicestaskforce.org/uspstf/uspscolo.htm |title=Screening for Colorectal Cancer |year=2008 |work=[[U.S. Preventive Services Task Force]]}}</ref> There is insufficient evidence to recommend for or against screening for [[skin cancer]],<ref>{{cite web |url=http://www.uspreventiveservicestaskforce.org/uspstf/uspsskca.htm |title=Screening for Skin Cancer |year=2009 |work=[[U.S. Preventive Services Task Force]]}}</ref> [[oral cancer]],<ref>{{cite web |url=http://www.uspreventiveservicestaskforce.org/uspstf/uspsoral.htm |title=Screening for Oral Cancer |year=2004 |work=[[U.S. Preventive Services Task Force]]}}</ref> [[lung cancer]],<ref>{{cite web |url=http://www.uspreventiveservicestaskforce.org/uspstf/uspslung.htm |title=Lung Cancer Screening |year=2004 |work=[[U.S. Preventive Services Task Force]]}}</ref> or [[prostate cancer]] in men under 75.<ref name=USPSTFPr08>{{cite web |url=http://www.uspreventiveservicestaskforce.org/uspstf/uspsprca.htm |title=Screening for Prostate Cancer |year=2008 |work=[[U.S. Preventive Services Task Force]]}}</ref> Routine screening is not recommended for [[bladder cancer]],<ref>{{cite web |url=http://www.uspreventiveservicestaskforce.org/uspstf/uspsblad.htm |title=Screening for Bladder Cancer |year=2004 |work=[[U.S. Preventive Services Task Force]]}}</ref> [[testicular cancer]],<ref>{{cite web |url=http://www.uspreventiveservicestaskforce.org/uspstf/uspstest.htm |title=Screening for Testicular Cancer |year=2004 |work=[[U.S. Preventive Services Task Force]]}}</ref> [[ovarian cancer]],<ref>{{cite web |url=http://www.uspreventiveservicestaskforce.org/uspstf/uspsovar.htm |title=Screening for Ovarian Cancer |year=2004 |work=[[U.S. Preventive Services Task Force]]}}</ref> [[pancreatic cancer]],<ref>{{cite web |url=http://www.uspreventiveservicestaskforce.org/uspstf/uspspanc.htm |title=Screening for Pancreatic Cancer |year=2004 |work=[[U.S. Preventive Services Task Force]]}}</ref> or [[prostate cancer]].<ref name="USPSTF-20111007">{{cite web |last1=Chou |first1=Roger |last2=Croswell |first2=Jennifer M. |last3=Dana |first3=Tracy |last4=Bougatous |first4=Christina |last5=Blazina |first5=Ian |last6=Fu |first6=Rongwei |last7=Gleitsmann |first7=Ken |last8=Koenig |first8=Helen C. |last9=Lam |first9=Clarence |last10=Maltz |first10=Ashley |last11=Rugge |first11=J. Bruin |last12=Lin |first12=Kenneth |title=Screening for Prostate Cancer: A Review of the Evidence for the U.S. Preventive Services Task Force |url=http://www.uspreventiveservicestaskforce.org/uspstf12/prostate/prostateart.htm |date=7 October 2011 |publisher=[[United States Preventive Services Task Force]] |accessdate=8 October 2011}}</ref>
-The USPSTF recommends [[mammography]] for [[breast cancer]] screening every two years for those 50–74&nbsp;years old; however, they do not recommend either [[breast self-examination]] or [[clinical breast examination]].<ref name=USPSTFBr09>{{cite web |url=http://www.uspreventiveservicestaskforce.org/uspstf/uspsbrca.htm |title=Screening for Breast Cancer |year=2009 |work=[[U.S. Preventive Services Task Force]]}}</ref> A 2011 [[Cochrane review]] came to slightly different conclusions with respect to breast cancer screening stating that routine mammography may do more harm than good.<ref name="CD001877">{{cite journal | author = Gøtzsche PC, Nielsen M | title = Screening for breast cancer with mammography | journal = Cochrane Database Syst Rev | volume = | issue = 1 | pages = CD001877 | year = 2011 | pmid = 21249649 | doi = 10.1002/14651858.CD001877.pub4 }}</ref>
-Japan screens for [[gastric cancer]] using [[photofluorography]] due to the high incidence there.<ref name=Epi11/>
-===Genetic testing===
-{{See also|Cancer syndrome}}
-{| class="wikitable" style="float:right; margin-left:15px; text-align:center"
-|-
-! Gene
-! Cancer types
-|-
-| [[BRCA1]], [[BRCA2]]
-| Breast, ovarian, pancreatic
-|-
-| [[HNPCC]], [[MLH1]], [[MSH2]], [[MSH6]], [[PMS1]], [[PMS2]]
-| Colon, uterine, small bowel, stomach, urinary tract
-|}
-[[Genetic testing]] for individuals at high-risk of certain cancers is recommended.<ref name=BRCA08>{{cite journal | author = Gulati AP, Domchek, SM | title = The clinical management of BRCA1 and BRCA2 mutation carriers | journal = Current oncology reports | volume = 10 | issue = 1 | pages = 47–53 | year = 2008 | month = Jan | pmid = 18366960 | doi = 10.1007/s11912-008-0008-9 }}</ref> Carriers of these mutations may than undergo enhanced surveillance, chemoprevention, or preventative surgery to reduce their subsequent risk.<ref name=BRCA08/>
-==Management==
-{{Main|Management of cancer}}
-Many management options for cancer exist with the primary ones including [[surgery]], [[chemotherapy]], [[radiation therapy]], and [[palliative care]]. Which treatments are used depends upon the type, location and grade of the cancer as well as the person's health and wishes.
-===Palliative care===
-[[Palliative care]] refers to treatment which attempts to make the patient feel better and may or may not be combined with an attempt to attack the cancer. Palliative care includes action to reduce the physical, emotional, spiritual, and psycho-social distress experienced by people with cancer. Unlike treatment that is aimed at directly killing cancer cells, the primary goal of palliative care is to improve the patient's [[quality of life (healthcare)|quality of life]].
-Patients at all stages of cancer treatment need some kind of palliative care to comfort them. In some cases, [[Specialty (medicine)|medical specialty]] [[professional organizations]] recommend that patients and physicians respond to cancer only with palliative care and not with cancer-directed therapy.<ref name="ASCOfive">{{Citation |author1 = American Society of Clinical Oncology |author1-link = American Society of Clinical Oncology |date = |title = Five Things Physicians and Patients Should Question |publisher = [[American Society of Clinical Oncology]] |work = Choosing Wisely: an initiative of the [[ABIM Foundation]] |page = |url = http://choosingwisely.org/wp-content/uploads/2012/04/5things_12_factsheet_Amer_Soc_Clin_Onc.pdf |accessdate = August 14 2012}}</ref> Those cases have the following characteristics:<ref>
-*The American Society of Clinical Oncology made this recommendation based on various cancers. See {{Citation |author1 = American Society of Clinical Oncology |author1-link = American Society of Clinical Oncology |date = |title = Five Things Physicians and Patients Should Question |publisher = [[American Society of Clinical Oncology]] |work = Choosing Wisely: an initiative of the [[ABIM Foundation]] |page = |url = http://choosingwisely.org/wp-content/uploads/2012/04/5things_12_factsheet_Amer_Soc_Clin_Onc.pdf |accessdate = August 14 2012}}
-*for lung cancer, see {{cite PMID|21900105}} and {{cite PMID|20679538}}
-*for breast cancer, see {{cite PMID|19200416}}
-*for colon cancer, see {{cite PMID|19755046}}
-*for other general statements see {{cite doi|10.1056/NEJMsb1013826}} and {{cite doi|10.1200/JCO.2010.33.1744}}</ref>
-#patient has low [[performance status]], corresponding with limited ability to care for oneself<ref name="ASCOfive"/>
-#patient received no benefit from prior [[Evidence-based medicine|evidence-based treatments]]<ref name="ASCOfive"/>
-#patient is ineligible to participate in any appropriate [[clinical trial]]<ref name="ASCOfive"/>
-#the physician sees no strong evidence that treatment would be effective<ref name="ASCOfive"/>
-Palliative care is often confused with [[hospice]] and therefore only involved when people approach [[End-of-life care|end of life]]. Like hospice care, palliative care attempts to help the person cope with the immediate needs and to increase the person's comfort. Unlike hospice care, palliative care does not require people to stop treatment aimed at prolonging their lives or curing the cancer.
-Multiple national [[medical guideline]]s recommend early palliative care for people whose cancer has produced distressing symptoms (pain, shortness of breath, fatigue, nausea) or who need help coping with their illness. In people who have metastatic disease when first diagnosed, oncologists should consider a palliative care consult immediately. Additionally, an oncologist should consider a palliative care consult in any patient they feel has a prognosis of less than 12 months even if continuing aggressive treatment.<ref>{{cite web|url=http://www.nccn.org/professionals/physician_gls/default.asp |title=NCCN Guidelines}}</ref><ref>{{cite web |url=http://www.nationalconsensusproject.org/guideline.pdf |title=Clinical Practice Guidelines for Quality Palliative Care |publisher = The National Consensus Project for Quality Palliative Care (NCP)}}</ref><ref>{{cite journal | author = Levy MH, Back, A, Bazargan, S, Benedetti, C, Billings, JA, Block, S, Bruera, E, Carducci, MA, Dy, S, Eberle, C, Foley, KM, Harris, JD, Knight, SJ, Milch, R, Rhiner, M, Slatkin, NE, Spiegel, D, Sutton, L, Urba, S, Von Roenn, JH, Weinstein, SM, National Comprehensive Cancer Network | title = Palliative care. Clinical practice guidelines in oncology | journal = Journal of the National Comprehensive Cancer Network: JNCCN | volume = 4 | issue = 8 | pages = 776–818 | year = 2006 | month = September | pmid = 16948956 | doi = }}</ref>
-===Surgery===
-Surgery is the primary method of treatment of most isolated solid cancers and may play a role in palliation and prolongation of survival.<!--<ref name=HollandTx40/> --> It is typically an important part of making the definitive diagnosis and [[cancer staging|staging the tumor]] as biopsies are usually required.<!--<ref name=HollandTx40/> --> In localized cancer surgery typically attempts to remove the entire mass along with, in certain cases, the [[lymph nodes]] in the area.<!--<ref name=HollandTx40/> --> For some types of cancer this is all that is needed to eliminate the cancer.<ref name=HollandTx40>Holland Chp. 40</ref>
-===Chemotherapy===
-[[Chemotherapy]] in addition to surgery has proven useful in a number of different cancer types including: [[breast cancer]], colorectal cancer, [[pancreatic cancer]], [[osteogenic sarcoma]], [[testicular cancer]], ovarian cancer, and certain lung cancers.<ref name=HollandTx40/> The effectiveness of chemotherapy is often limited by toxicity to other tissues in the body.
-===Radiation===
-[[Radiation therapy]] involves the use of [[ionizing radiation]] in an attempt to either cure or improve the symptoms of cancer.<!--<ref name=H41/> --> It is used in about half of all cases and the radiation can be from either internal sources in the form of [[brachytherapy]] or external sources.<!--<ref name=H41/> --> Radiation is typically used in addition to surgery and or chemotherapy but for certain types of cancer such as early [[head and neck cancer]] may be used alone.<!--<ref name=H41/> --> For painful [[bone metastasis]] it has been found to be effective in about 70% of people.<ref name=H41>Holland Chp. 41</ref>
-===Alternative treatments===
-[[Alternative cancer treatments|Complementary and alternative cancer treatments]] are a diverse group of health care systems, practices, and products that are not part of conventional medicine.<ref name="mnalt">{{cite journal | author = Cassileth BR, Deng G | title = Complementary and alternative therapies for cancer | journal = Oncologist | volume = 9 | issue = 1 | pages = 80–9 | year = 2004 | pmid = 14755017 | doi = 10.1634/theoncologist.9-1-80 }}</ref> "Complementary medicine" refers to methods and substances used along with conventional medicine, while "alternative medicine" refers to compounds used instead of conventional medicine.<ref>[http://nccam.nih.gov/health/whatiscam/#2 What Is CAM?] [[National Center for Complementary and Alternative Medicine]]. retrieved 3 February 2008.</ref> Most complementary and alternative medicines for cancer have not been rigorously studied or tested. Some alternative treatments have been investigated and shown to be ineffective but still continue to be marketed and promoted.<ref name="pmid15061600">{{cite journal | author = Vickers A | title = Alternative cancer cures: 'unproven' or 'disproven'? | journal = CA Cancer J Clin | volume = 54 | issue = 2 | pages = 110–8 | year = 2004 | pmid = 15061600 | doi = 10.3322/canjclin.54.2.110 }}</ref>
-==Prognosis==
-{{See also|Cancer survivor}}
-Cancer has a reputation as a deadly disease. Taken as a whole, about half of people receiving treatment for invasive cancer (excluding [[carcinoma in situ]] and non-melanoma skin cancers) die from cancer or its treatment.<ref name=Epi11/> Survival is worse in the developing world.<ref name=Epi11/> However, the survival rates vary dramatically by type of cancer, with the range running from basically all people surviving to almost no one surviving.
-Those who survive cancer are at increased risk of developing a second primary cancer at about twice the rate of those never diagnosed with cancer.<ref name="isbn1-55009-213-8" /> The increased risk is believed to be primarily due to the same risk factors that produced the first cancer, partly due to the treatment for the first cancer, and potentially related to better compliance with screening.<ref name="isbn1-55009-213-8">{{cite book| editor=Frei, Emil; Kufe, Donald W.; Holland, James F.|author=Rheingold, Susan; Neugut, Alfred; Meadows, Anna| title=Holland-Frei Cancer Medicine| edition = 6th| publisher=BC Decker| location=Hamilton, Ont| year=2003| page=2399| isbn=1-55009-213-8|chapterurl=http://www.ncbi.nlm.nih.gov/books/NBK20948/| chapter=156: Secondary Cancers: Incidence, Risk Factors, and Management| accessdate=5 November 2009}}</ref>
-Predicting either short-term or long-term survival is difficult and depends on many factors. The most important factors are the particular kind of cancer and the patient's age and overall health. People who are [[wikt:frailty|frail]] with many other health problems have lower survival rates than otherwise healthy people. A [[centenarian]] is unlikely to survive for five years even if the treatment is successful. People who report a higher quality of life tend to survive longer.<ref>{{cite journal | author = Montazeri A | title = Quality of life data as prognostic indicators of survival in cancer patients: an overview of the literature from 1982 to 2008 | journal = Health Qual Life Outcomes | volume = 7 | issue = | pages = | year = 2009 | month = December | pmid = 20030832 | pmc = 2805623 | doi = 10.1186/1477-7525-7-102 }}</ref> People with lower quality of life may be affected by [[major depressive disorder]] and other complications from cancer treatment and/or disease progression that both impairs their quality of life and reduces their quantity of life. Additionally, patients with worse prognoses may be depressed or report a lower quality of life directly because they correctly perceive that their condition is likely to be fatal.
-==Epidemiology==
-{{Main|Epidemiology of cancer}}
-[[Image:Malignant neoplasms world map - Death - WHO2004.svg|thumb|Death rate from malignant cancer per 100,000&nbsp;inhabitants in 2004.<ref>{{cite web |url=http://www.who.int/healthinfo/global_burden_disease/estimates_country/en/index.html |title=WHO Disease and injury country estimates |year=2009 |work=World Health Organization |accessdate=11 November 2009}}</ref>
-{{Multicol}}
-{{legend|#b3b3b3|no data}}
-{{legend|#ffff65|≤&nbsp;55}}
-{{legend|#fff200|55–80}}
-{{legend|#ffdc00|80–105}}
-{{legend|#ffc600|105–130}}
-{{legend|#ffb000|130–155}}
-{{legend|#ff9a00|155–180}}
-{{Multicol-break}}
-{{legend|#ff8400|180–205}}
-{{legend|#ff6e00|205–230}}
-{{legend|#ff5800|230–255}}
-{{legend|#ff4200|255–280}}
-{{legend|#ff2c00|280–305}}
-{{legend|#cb0000|≥&nbsp;305}}
-{{Multicol-end}} ]]
-In 2008 approximately 12.7&nbsp;million cancers were [[diagnosed]] (excluding [[non-melanoma skin cancer]]s and other non-invasive cancers) and 7.6&nbsp;million people died of cancer worldwide.<ref name=Epi11>{{cite journal | author = Jemal A, Bray, F, Center, MM, Ferlay, J, Ward, E, Forman, D | title = Global cancer statistics | journal = CA: a cancer journal for clinicians | volume = 61 | issue = 2 | pages = 69–90 | year = 2011 | month = February | pmid = 21296855 | doi = 10.3322/caac.20107 }}</ref> Cancers as a group account for approximately 13% of all deaths each year with the most common being: [[lung cancer]] (1.4 million deaths), [[stomach cancer]] (740,000 deaths), [[liver cancer]] (700,000 deaths), [[colorectal cancer]] (610,000 deaths), and [[breast cancer]] (460,000 deaths).<ref name="WHO">{{cite web | last =WHO | authorlink =World Health Organization | title =Cancer | publisher =World Health Organization |month=October | year=2010 | url =http://www.who.int/mediacentre/factsheets/fs297/en/ | accessdate =5 January 2011}}</ref> This makes invasive cancer the leading cause of death in the [[developed world]] and the second leading cause of death in the [[developing world]].<ref name=Epi11/> Over half of cases occur in the developing world.<ref name=Epi11/>
-Global cancer rates have been increasing primarily due to an aging population and lifestyle changes in the developing world.<ref name=Epi11/> The most significant [[risk factor]] for developing cancer is old age.<ref name=Coleman>{{cite book|author=Coleman, William B. and Rubinas, Tara C.|editor=Tsongalis, Gregory J. and Coleman, William L.|title=Molecular Pathology: The Molecular Basis of Human Disease|publisher=Elsevier Academic Press|location=Amsterdam|year=2009|page=66|chapter=4|isbn=0-12-374419-9|oclc=}}</ref> Although it is possible for cancer to strike at any age, most people who are diagnosed with invasive cancer are over the age of 65.<ref name=Coleman /> According to cancer researcher [[Robert A. Weinberg]], "If we lived long enough, sooner or later we all would get cancer."<ref name=Weinberg>{{cite news| url = http://www.nytimes.com/2010/12/28/health/28cancer.html| title = Unearthing Prehistoric Tumors, and Debate| newspaper = [[The New York Times]]| date = 28 December 2010| author = Johnson, George}}</ref> Some of the association between aging and cancer is attributed to [[immunosenescence]],<ref>{{cite journal | author = Pawelec G, Derhovanessian, E, Larbi, A | title = Immunosenescence and cancer | journal = Critical reviews in oncology/hematology | volume = 75 | issue = 2 | pages = 165–72 | year = 2010 | month = Aug | pmid = 20656212 | doi = 10.1016/j.critrevonc.2010.06.012 }}</ref> errors accumulated in [[DNA]] over a lifetime,<ref>{{cite book
-|author=Alberts, B, Johnson A, Lewis J, et al.
-|title=Molecular biology of the cell
-|publisher=Garland Science
-|location=New York
-|year=2002
-|edition=4th
-|chapter=The Preventable Causes of Cancer
-|isbn=0-8153-4072-9
-|url=http://www.ncbi.nlm.nih.gov/books/NBK26897/
-|quote=A certain irreducible background incidence of cancer is to be expected regardless of circumstances: mutations can never be absolutely avoided, because they are an inescapable consequence of fundamental limitations on the accuracy of DNA replication, as discussed in Chapter 5. If a human could live long enough, it is inevitable that at least one of his or her cells would eventually accumulate a set of mutations sufficient for cancer to develop.
-|oclc=
-|doi= }}</ref> and age-related changes in the endocrine system.<ref>{{cite journal | author = Anisimov VN, Sikora, E, Pawelec, G | title = Relationships between cancer and aging: a multilevel approach | journal = Biogerontology | volume = 10 | issue = 4 | pages = 323–38 | year = 2009 | month = Aug | pmid = 19156531 | doi = 10.1007/s10522-008-9209-8 }}</ref>
-Some slow-growing cancers are particularly common. [[Autopsy]] studies in Europe and Asia have shown that up to 36% of people have undiagnosed and apparently harmless [[thyroid cancer]] at the time of their deaths, and that 80% of men develop [[prostate cancer]] by age 80.<ref>{{cite book| author = Fraumeni, Joseph F.; Schottenfeld, David; Marshall, James M.| title = Cancer epidemiology and prevention| publisher = Oxford University Press| location = Oxford [Oxfordshire]| year = 2006| page = 977| isbn = 0-19-514961-0| oclc =}}</ref><ref>{{cite book| author = Bostwick, David G.; Eble, John N.| title = Urological Surgical Pathology| publisher = Mosby| location = St. Louis| year = 2007| page = 468| isbn = 0-323-01970-6| oclc =}}</ref> As these cancers did not cause the person's death, identifying them would have represented [[overdiagnosis]] rather than useful medical care.
-The three most common [[childhood cancer]]s are [[leukemia]] (34%), [[brain tumor]]s (23%), and [[lymphoma]]s (12%).<ref name=Euro10>{{cite journal | author = Kaatsch P, Sikora, E, Pawelec, G | title = Epidemiology of childhood cancer | journal = Cancer treatment reviews | volume = 36 | issue = 4 | pages = 277–85 | year = 2010 | month = June | pmid = 20231056 | doi = 10.1016/j.ctrv.2010.02.003 }}</ref>  Rates of childhood cancer have increased by 0.6% per year between 1975 to 2002 in the United States<ref>{{cite journal | author = Ward EM, Thun, MJ, Hannan, LM, Jemal, A | title = Interpreting cancer trends | journal = Annals of the New York Academy of Sciences | volume = 1076 | issue = | pages = 29–53 | year = 2006 | month = Sep | pmid = 17119192 | doi = 10.1196/annals.1371.048 | bibcode = 2006NYASA1076...29W }}</ref> and by 1.1% per year between 1978 and 1997 in Europe.<ref name=Euro10/>
-==History==
-{{Main|History of cancer}}
-[[File:Clara Jacobi-Tumor.jpg|thumb|[[Engraving]] with two views of a Dutch woman who had a tumor removed from her neck in 1689.]]
-The earliest written record regarding cancer is from 3000 BC in the Egyptian [[Edwin Smith Papyrus]] and describes cancer of the breast.<ref name=Hist1>{{cite journal | author = Hajdu SI, Thun, MJ, Hannan, LM, Jemal, A | title = A note from history: landmarks in history of cancer, part 1. | journal = Cancer | volume = 117 | issue = 5 | pages = 1097–102 | year = 2011 | month = March | pmid = 20960499 | doi = 10.1002/cncr.25553 }}</ref> Cancer however has existed for all of human history.<ref name=Hist1/> [[Hippocrates]] (ca. 460 BC – ca. 370 BC) described several kinds of cancer, referring to them with the [[Greek language|Greek]] word ''carcinos'' ([[crab]] or [[crayfish]]).<ref name=Hist1/> This name comes from the appearance of the cut surface of a solid malignant tumour, with "the veins stretched on all sides as the animal the crab has its feet, whence it derives its name".<ref>Paul of Aegina, 7th Century AD, quoted in {{cite web| first = Ralph W.| last = Moss| title = Galen on Cancer| url = http://www.cancerdecisions.com/speeches/galen1989.html| archiveurl = http://web.archive.org/web/20110716111312/http://www.cancerdecisions.com/speeches/galen1989.html| archivedate = 16 July 2011| publisher = CancerDecisions| year = 2004}} Referenced from Michael Shimkin, Contrary to Nature, Washington, D.C.: Superintendent of Document, DHEW Publication No. (NIH) 79-720, p. 35.</ref> [[Aulus Cornelius Celsus|Celsus]] (ca. 25 BC – 50 AD) translated ''carcinos'' into the [[Latin]] ''cancer'', also meaning crab and recommended surgery as treatment.<ref name=Hist1/> [[Galen]] (2nd century AD) disagreed with the use of surgery and recommended [[purgatives]] instead.<ref name=Hist1/> These recommendations largely stood for 1000 years.<ref name=Hist1/>
-In the 15th, 16th and 17th centuries, it became more acceptable for doctors to [[autopsy|dissect bodies]] to discover the cause of death.<ref name=Hist2>{{cite journal | author = Hajdu SI, Thun, MJ, Hannan, LM, Jemal, A | title = A note from history: landmarks in history of cancer, part 2. | journal = Cancer | volume = 117 | issue = 12 | pages = 2811–20 | year = 2011 | month = June | pmid = 21656759 | doi = 10.1002/cncr.25825 }}</ref> The German professor [[Wilhelm Fabry]] believed that breast cancer was caused by a milk clot in a mammary duct. The Dutch professor [[Francois de la Boe Sylvius]], a follower of [[Descartes]], believed that all disease was the outcome of chemical processes, and that acidic [[lymph]] fluid was the cause of cancer. His contemporary [[Nicolaes Tulp]] believed that cancer was a poison that slowly spreads, and concluded that it was [[infectious disease|contagious]].<ref>{{cite book|last=Yalom|first=Marilyn|title=A history of the breast|year=1998|publisher=Ballantine Books|location=New York|isbn=0-679-43459-3|edition=1st Ballantine Books ed.}}</ref>
-The physician John Hill described tobacco snuff as the cause of nose cancer in 1761.<ref name=Hist2/> This was followed by the report in 1775 by British surgeon [[Percivall Pott]] that cancer of the [[scrotum]] was a common disease among [[chimney sweep]]s.<ref>{{cite journal | author = Hajdu SI, Thun, MJ, Hannan, LM, Jemal, A | title = A note from history: Landmarks in history of cancer, part 3. | journal = Cancer | volume = 118 | issue = 4 | pages = 1155–68 | year = 2011 | month = July | pmid = 21751192 | doi = 10.1002/cncr.26320 }}</ref> With the widespread use of the microscope in the 18th century, it was discovered that the 'cancer poison' spread from the primary tumor through the lymph nodes to other sites ("[[metastasis]]"). This view of the disease was first formulated by the English surgeon [[Campbell De Morgan]] between 1871 and 1874.<ref>{{cite journal | author = Grange JM, Stanford JL, Stanford CA | title = Campbell De Morgan's 'Observations on cancer', and their relevance today | journal = Journal of the Royal Society of Medicine | volume = 95 | issue = 6 | pages = 296–9 | year = 2002 | pmid = 12042378 | pmc = 1279913 | doi = 10.1258/jrsm.95.6.296 }}</ref>
-==Society and culture==
-Though many diseases (such as [[heart failure]]) may have a worse prognosis than most cases of cancer, cancer is the subject of widespread fear and taboos. The [[euphemism]], "after a long illness" is still commonly used (2012), reflecting an apparent [[social stigma|stigma]].<ref>{{Cite news
-| first = Barbara
-| last = Ehrenreich
-| authorlink = Barbara Ehrenreich
-| title = Welcome to Cancerland
-| newspaper = [[Harper's Magazine]]
-| date = November 2001
-| issn = 0017-789X
-| url = http://www.barbaraehrenreich.com/cancerland.htm}}</ref> This deep belief that cancer is necessarily a difficult and usually deadly disease is reflected in the systems chosen by society to compile cancer statistics: the most common form of cancer—non-melanoma [[skin cancer]]s, accounting for about one-third of all cancer cases worldwide, but very few deaths<ref name="Bolognia">{{cite book |author=Rapini, Ronald P.; Bolognia, Jean L.; Jorizzo, Joseph L. |title=Dermatology: 2-Volume Set |publisher=Mosby |location=St. Louis |year=2007 |pages= |isbn=1-4160-2999-0 |oclc= |doi=}}</ref><ref>{{cite web
-| title = Skin cancers
-| url = http://www.who.int/uv/faq/skincancer/en/index1.html
-| publisher = World Health Organization
-| accessdate = 19 January 2011}}</ref>—are excluded from cancer statistics specifically because they are easily treated and almost always cured, often in a single, short, outpatient procedure.<ref>{{cite book
-|author=McCulley, Michelle; Greenwell, Pamela
-|title=Molecular therapeutics: 21st-century medicine
-|publisher=J. Wiley
-|location=London
-|year=2007
-|page= 207
-|isbn=0-470-01916-6
-|oclc=}}</ref>
-Cancer is regarded as a disease that must be "fought" to end the "civil insurrection"; a [[War on Cancer]] has been declared. Military metaphors are particularly common in descriptions of cancer's human effects, and they emphasize both the parlous state of the affected individual's health and the need for the individual to take immediate, decisive actions himself, rather than to delay, to ignore, or to rely entirely on others caring for him. The military metaphors also help rationalize radical, destructive treatments.<ref name=Gwyn>{{cite book
-| author=Gwyn, Richard
-| editor=Cameron, Lynne; Low, Graham
-| title=Researching and applying metaphor
-| publisher=Cambridge University Press
-| location=Cambridge, UK
-| year=1999
-| chapter=10
-| isbn=0-521-64964-1}}</ref><ref>{{cite book
-| author=Sulik, Gayle
-| title=Pink Ribbon Blues: How Breast Cancer Culture Undermines Women's Health
-| publisher=Oxford University Press
-| location=New York
-| year=2010
-| oclc = 535493589
-| isbn=0-19-974045-3
-| pages=78–89}}</ref> <!-- Both refs apply to the whole paragraph -->
-In the 1970s, a relatively popular [[alternative cancer treatment]] was a specialized form of [[talk therapy]], based on the idea that cancer was caused by a bad attitude.<ref name=Olson /> People with a "cancer personality"—depressed, repressed, self-loathing, and afraid to express their emotions—were believed to have manifested cancer through subconscious desire. Some psychotherapists said that treatment to change the patient's outlook on life would cure the cancer.<ref name=Olson /> Among other effects, this belief allows society to [[blame the victim]] for having caused the cancer (by "wanting" it) or having prevented its cure (by not becoming a sufficiently happy, fearless, and loving person).<ref name=Ehrenreich /> It also increases patients' anxiety, as they incorrectly believe that natural emotions of sadness, anger or fear shorten their lives.<ref name=Ehrenreich /> The idea was excoriated by the notoriously outspoken [[Susan Sontag]], who published ''[[Illness as Metaphor]]'' while recovering from treatment for [[breast cancer]] in 1978.<ref name=Olson>{{cite book
-| author=Olson, James Stuart
-| title=Bathsheba's Breast: Women, Cancer and History
-| publisher=The Johns Hopkins University Press
-| location=Baltimore
-| year=2002
-| pages = 145–170
-| oclc = 186453370
-| isbn=0-8018-6936-6}}</ref> Although the original idea is now generally regarded as nonsense, the idea partly persists in a reduced form with a widespread, but incorrect, belief that deliberately cultivating a habit of [[positive thinking]] will increase survival.<ref name=Ehrenreich>{{cite book
-|author=Ehrenreich, Barbara
-|title=Bright-sided: How the Relentless Promotion of Positive Thinking Has Undermined America
-|publisher=Metropolitan Books
-|location=New York
-|year=2009
-|pages=15–44
-|isbn=0-8050-8749-4
-|oclc=}}</ref> This notion is particularly strong in [[breast cancer culture]].<ref name=Ehrenreich />
-In 2007, the overall costs of cancer in the U.S. — including treatment and indirect mortality expenses (such as lost productivity in the workplace) — was estimated to be $226.8 billion. In 2009, 32% of Hispanics and 10% of children 17 years old or younger lacked health insurance; "uninsured patients and those from ethnic minorities are substantially more likely to be diagnosed with cancer at a later stage, when treatment can be more extensive and more costly."<ref>{{cite web|url = http://journalistsresource.org/studies/society/health/cancer-facts-figures-2012/ |title = Cancer Facts and Figures 2012 |publisher = Journalist's Resource.org }}</ref>
-==Research==
-{{Main|Cancer research}}
-Because cancer is a class of diseases,<ref name=WhatIsCancerNCI>{{cite web| url=http://www.cancer.gov/cancertopics/what-is-cancer| title=What Is Cancer?| publisher=[[National Cancer Institute]]| accessdate=17 August 2009}}</ref><ref>{{cite web|url=http://www.atsdr.cdc.gov/COM/cancer-fs.html| title=Cancer Fact Sheet| publisher=Agency for Toxic Substances &amp; Disease Registry|date=30 August 2002| accessdate=17 August 2009}}</ref> it is unlikely that there will ever be a single "[[cure for cancer]]" any more than there will be a single treatment for all [[infectious disease]]s.<ref>{{cite web| url=http://www.livescience.com/health/060919_bad_cancer.html|title=Exciting New Cancer Treatments Emerge Amid Persistent Myths| last=Wanjek| first= Christopher| date=16 September 2006|accessdate=17 August 2009}}</ref> [[Angiogenesis inhibitors]] were once thought to have potential as a "[[silver bullet]]" treatment applicable to many types of cancer, but this has not been the case in practice.<ref>{{cite journal | author = Hayden EC, Thun, MJ, Hannan, LM, Jemal, A | title = Cutting off cancer's supply lines | journal = Nature | volume = 458 | issue = 7239 | pages = 686–687 | year = 2009 | month = April | pmid = 19360048 | doi = 10.1038/458686b }}</ref>
-[[Experimental cancer treatment]]s are treatments that are being studied to see whether they work. Typically, these are studied in [[clinical trial]]s to compare the proposed treatment to the best existing treatment. They may be entirely new treatments, or they may be treatments that have been used successfully in one type of cancer, and are now being tested to see whether they are effective in another type.<ref>{{cite journal | author = Sleigh SH, Barton CL | title = Repurposing Strategies for Therapeutics | journal = Pharm Med | volume = 24 | issue = 3 | pages = 151–159 | year = 2010 | pmid = | doi = 10.2165/11536770-000000000-00000 }}</ref> More and more, such treatments are being developed alongside companion diagnostic tests to target the right drugs to the right patients, based on their individual biology.<ref>{{cite journal | author = Winther H, Jorgensen JT | title = Drug-Diagnostic Co-Development in Cancer | journal = Pharm Med | volume = 24 | issue = 6 | pages = 363–375 | year = 2010 | pmid = | doi = 10.2165/11586320-000000000-00000 }}</ref>
-Cancer research is the intense scientific effort to understand disease processes and discover possible therapies.
-Research about cancer causes focuses on the following issues:
-* Agents (e.g. viruses) and events (e.g. mutations) which cause or facilitate genetic changes in cells destined to become cancer.
-* The precise nature of the genetic damage, and the genes which are affected by it.
-* The consequences of those genetic changes on the biology of the cell, both in generating the defining properties of a cancer cell, and in facilitating additional genetic events which lead to further progression of the cancer.
-The improved understanding of [[molecular biology]] and [[cellular biology]] due to cancer research has led to a number of new treatments for cancer since U.S. President Nixon declared the "[[War on Cancer]]" in 1971. Since then, the U.S. has spent over $200 billion on cancer research, including resources from the public and private sectors and foundations.<ref>{{cite web |author=Sharon Begley | url=http://www.newsweek.com/id/157548/page/2 |title=Rethinking the War on Cancer |date=16 September 2008 | work=Newsweek |accessdate=8 September 2008}}</ref> During that time, the country has seen a five percent decrease in the cancer death rate (adjusting for size and age of the population) between 1950 and 2005.<ref>{{cite news|url=http://www.nytimes.com/2009/04/24/health/policy/24cancer.html |title=Advances Elusive in the Drive to Cure Cancer |last=Kolata|first=Gina|authorlink=Gina Kolata|date=23 April 2009 |work=[[The New York Times]]|accessdate=5 May 2009}}</ref>
-==Pregnancy==
-Because cancer is largely a disease of older adults, it is not common in pregnant women. Cancer affects approximately 1 in 1,000 pregnant women.<ref name=yarbro /> The most common cancers found during pregnancy are the same as the most common cancers found in non-pregnant women during childbearing ages: breast cancer, cervical cancer, leukemia, lymphoma, melanoma, ovarian cancer, and colorectal cancer.<ref name=yarbro />
-Diagnosing a new cancer in a pregnant woman is difficult, in part because any symptoms are commonly assumed to be a normal discomfort associated with pregnancy.<ref name=yarbro /> As a result, cancer is typically discovered at a somewhat later stage than average in many pregnant or recently pregnant women. Some imaging procedures, such as [[MRI]]s (magnetic resonance imaging), [[CT scan]]s, ultrasounds, and [[mammogram]]s with fetal shielding are considered safe during pregnancy; some others, such as [[PET scan]]s are not.<ref name=yarbro />
-Treatment is generally the same as for non-pregnant women.<ref name=yarbro /> However, radiation and radioactive drugs are normally avoided during pregnancy, especially if the fetal dose might exceed 100 cGy. In some cases, some or all treatments are postponed until after birth if the cancer is diagnosed late in the pregnancy. Early deliveries to speed the start of treatment are not uncommon. Surgery is generally safe, but pelvic surgeries during the first trimester may cause miscarriage. Some treatments, especially certain chemotherapy drugs given during the [[first trimester]], increase the risk of [[birth defect]]s and [[pregnancy loss]] (spontaneous abortions and stillbirths).<ref name=yarbro />
-Elective [[abortion]]s are not required and, for the most common forms and stages of cancer, do not improve the likelihood of the mother surviving or being cured.<ref name=yarbro /> In a few instances, such as advanced uterine cancer, the pregnancy cannot be continued, and in others, such as an acute leukemia discovered early in pregnancy, the pregnant woman may choose to have abortion so that she can begin aggressive chemotherapy without worrying about birth defects.<ref name=yarbro />
-Some treatments may interfere with the mother's ability to give birth vaginally or to breastfeed her baby.<ref name=yarbro /> Cervical cancer may require birth by Caesarean section. Radiation to the breast reduces the ability of that breast to produce milk and increases the risk of [[mastitis]]. Also, when chemotherapy is being given after birth, many of the drugs pass through breast milk to the baby, which could harm the baby.<ref name=yarbro>{{cite book
-| title = Cancer nursing: principles and practice
-| editor = Connie Henke Yarbro, Debra Wujcik, Barbara Holmes Gobel
-| edition = 7
-| publisher= Jones & Bartlett Publishers
-| year = 2011
-| isbn = 978-1-4496-1829-2
-| pages = 901–905}}</ref>
-==Other animals==
-In non-humans, a few types of [[transmissible cancer]] have been described, wherein the cancer spreads between animals by transmission of the tumor cells themselves. This phenomenon is seen in dogs with [[Sticker's sarcoma]], also known as canine transmissible venereal tumor,<ref name="pmid16901782">{{cite journal | author = Murgia C, Pritchard JK, Kim SY, Fassati A, Weiss RA | title = Clonal origin and evolution of a transmissible cancer | journal = Cell | volume = 126 |issue = 3 | pages = 477–87 | year = 2006 | month = August | pmid = 16901782 | pmc = 2593932 | doi = 10.1016/j.cell.2006.05.051 }}</ref> as well as [[devil facial tumour disease]] in [[Tasmanian devil]]s.
-==Notes==
-{{Reflist|2}}
-;References
-* {{cite book|last=Holland|first=James F.|title=Holland-Frei cancer medicine.|year=2009|publisher=McGraw-Hill Medical|location=New York|isbn=978-1-60795-014-1|edition=8th ed.}}
-==Further reading==
-* {{cite book|last=Kleinsmith|first=Lewis J.|title=Principles of cancer biology|url=http://books.google.com/books?id=LKVrAAAAMAAJ|year=2006|publisher=Pearson Benjamin Cummings|isbn=978-0-8053-4003-7}}
-* {{cite book|last=Mukherjee|first=Siddhartha|authorlink=Siddhartha Mukherjee|title=[[The Emperor of All Maladies: A Biography of Cancer]]|accessdate=6 September 2011|date=16 November 2010|publisher=Simon and Schuster|isbn=978-1-4391-0795-9}}
-* {{cite book|last1=Pazdur|first1=Richard|author2=et al.|title=Cancer Management: A Multidisciplinary Approach|url=http://books.google.com/books?id=wbLnPAAACAAJ|date=May 2009|publisher=Cmp United Business Media|isbn=978-1-891483-62-2}} [http://www.cancernetwork.com/cancer-management-11 (online at cancernetwork.com)]
-* {{cite book|last=Tannock|first=Ian|title=The basic science of oncology|url=http://books.google.com/books?id=Bb4F4pj2BdYC|year=2005|publisher=McGraw-Hill Professional|isbn=978-0-07-138774-3}}
-* {{cite book |author=Manfred Schwab |title=Encyclopedia of Cancer (4 Volume Set) |publisher=Springer |location=Berlin |year=2008 |isbn=3-540-36847-7}}
-==External links==
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-{{Commons|Cancer}}
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-{{Carcinogen}}
-[[Category:Cancer| ]]
-[[Category:Aging-associated diseases]]
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