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Colon tumor

Familial polyposis syndromes of colon

Familial adenomatous polyposis of colon-attenuated FAP (AFAP)

Reviewers: Charanjeet Singh, M.D. (see Reviewers page)
Revised: 13 October 2011, last major update August 2011
Copyright: (c) 2003-2011, PathologyOutlines.com, Inc.

Clinical features

● Previously called hereditary flat adenoma syndrome (Dis Colon Rectum 1992;35:411, Fam Cancer 2003;2:43)
● Usually less than 100 polyps, but high risk for colorectal carcinoma (69% cumulative risk by age 80, Gastroenterology 2004;127:444)
● Phenotypically and genetically heterogeneous (Gut 2006;55:1440)
● Polyps usually more proximal (i.e. right sided) than in classic FAP; often rectal polyp sparing
● Cancers usually develop at age 50-55 years, 15 years later than classic FAP
● May develop stomach fundic gland polyps, gastric or small bowel flat adenomas and stomach / duodenal carcinomas (Cancer 1993;71:2709)
Diagnosis: genetic testing is important

Case reports

● 60 flat adenomas in proximal colon (Int J Gastrointest Cancer 2003;33:117)
● 2 early cases (Cancer 1990;66:909)
● 42 year old woman with presentation of ampullary adenoma (University of Pittsburgh)

Gross description

● Polyps are flat or slightly raised or plaque-like

Micro images

Tubular adenoma in colon of patient

Molecular description

● Germline mutations in 5' and 3' end and exon 9 of APC gene (also biallelic MUTYH mutations, Int J Cancer 2006;119:807)

Differential diagnosis

● Hereditary non-polyposis colon cancer: Am J Gastroenterol 2002;97:1822

End of Colon tumor > Familial polyposis syndromes of colon > Familial adenomatous polyposis of colon-attenuated FAP (AFAP)

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