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WHO Classification of Tumours
Adenocarcinoma, NOS
Colon and rectum


A common, malignant tumour characterized by the presence of malignant glandular cells. Morphologically, adenocarcinomas are classified according to the growth pattern (e.g., papillary, alveolar) or according to the secreted product (e.g., mucinous, serous). Representative examples of adenocarcinoma are ductal and lobular breast carcinoma, lung adenocarcinoma, renal cell adenocarcinoma, hepatocellular carcinoma, colon adenocarcinoma, and prostate adenocarcinoma.

Carcinoma of the colon and rectum
A malignant epithelial tumour originating in the large bowel. Metastasis, and therefore the use of the term “carcinoma” for tumours of the colon and rectum, requires invasion through the muscularis mucosae into the submucosa. More than 90% of colorectal carcinomas (CRC) are adenocarcinomas

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Boyle P, Levin B (eds.)
World Cancer Report.
Lyon 2008

. Higher rates occur in industrialized, high resource countries (about 40–60 per 100 000), The worldwide mortality rate is about half the incidence rate (about 608 000 deaths from CRC in 2002), but there is wide variation in mortality rates according to available treatment options, with lower rates in countries with high incidences and high resources
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Boyle P, Levin B (eds.)
World Cancer Report.
Lyon 2008

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Ferlay J, Bray F, Pisani P, Parkin M
Cancer incidence, Mortality and Prevalence Worldwide. Globocan 2002. IARCCancerBase No. 5
IARC: Lyon 2004

. Nonetheless, CRC is the most common cause of deaths from cancer that is not directly attributable to tobacco usage in some of these countries. A high incidence of CRC is observed consistently in populations with a “Westerntype” diet (highly caloric food rich in animal fat) combined with a sedentary lifestyle. Chronic inflammatory bowel diseases are also etiological factors for CRC
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Konda A, Duffy MC (2008)
Surveillance of patients at increased risk of colon cancer: inflammatory bowel disease and other conditions.
Gastroenterol Clin North Am 37: 191-213, viii

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Triantafillidis JK, Nasioulas G, Kosmidis PA (2009)
Colorectal cancer and inflammatory bowel disease: epidemiology, risk factors, mechanisms of carcinogenesis and prevention strategies.
Anticancer Res 29: 2727-37

, such as ulcerative colitis, Crohn disease, and Schistosoma mansoni infection
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Yosry A (2006)
Schistosomiasis and neoplasia.
Contrib Microbiol 13: 81-100

. Anatomic extent of disease, i.e. tumour stage, is the strongest prognostic factor for CRC. Other prognostic factors include the morphology, lymph node metastases, extend of resection, extramural veinous invasion and genes and biomarkers.

> Histological subtypes
Cribriform comedo-type adenocarcinoma
Medullary carcinoma
Micropapillary carcinoma
Mucoid adenocarcinoma
Serrated adenocarcinoma
Signet ring cell carcinoma

Carcinomas other than adenocarcinomas:
Adenosquamous carcinoma
Spindle cell carcinoma
Squamous cell carcinoma
Poorly differentiated carcinoma

Rare variants
There is an additional heterogeneous group of very rare CRC variants, e.g. clear cell carcinoma, that often have a component of conventional adenocarcinoma or mimic other types of cancers, e.g. choriocarcinoma

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Granier G, Marty-Double C (2007)
[Gastrointestinal adenocarcinomas with a choriocarcinomatous component: 2 cases and a review of 120 cases in the literature].
Gastroenterol Clin Biol 31: 854-7

, Paneth cell-rich papillary adenocarcinomas
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Shousha S (1979)
Paneth cell-rich papillary adenocarcinoma and a mucoid adenocarcinoma occurring synchronously in colon: a light and electron microscopic study.
Histopathology 3: 489-501

. The differential diagnosis includes metastasis from elsewhere or rare primary colorectal tumours, e.g. primary melanoma or nonepithelial cell types such as gastrointestinal stromal tumours (GISTs)
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Bosman FT, Carneiro F, Hruban RH, Theise ND (Eds.)
WHO Classification of Tumours of the Digestive System.
4th Edition
International Agency for Research on Cancer: Lyon 2010