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Colon tumor

Familial polyposis syndromes of colon

Familial adenomatous polyposis of colon-classic

Reviewers: Charanjeet Singh, M.D. (see Reviewers page)
Revised: 14 October 2011, last major update August 2011
Copyright: (c) 2003-2011, PathologyOutlines.com, Inc.

Clinical features

● Also known as familial polyposis coli
● Due to defect in APC gene at 5q21; polyposis patients without APC mutations often have mutations in MYH gene
● Autosomal dominant trait with high degree of penetrance
● Incidence of 1 per 8-30,000 individuals
● 20% represent a new mutation
● 100% progress to colonic adenocarcinoma, often in teens, most by thirties
● Patients have > 100 colon polyps (usually thousands), beginning as teenagers; most are tubular adenomas
● Polyps in children may have severe dysplasia (J Pediatr Surg 2006;41:658)
● Polyps may also occur in stomach (fundic gland polyps) and small intestine, although most ileal lesions are lymphoid hyperplasia not adenomas
● May also develop carcinoma of thyroid gland, gallbladder and adrenal gland; also desmoid tumors (10-25%)
● APC mutations may cause expansion of crypt base cell population, including crypt stem cells; mutant crypt stem cells may clonally expand to form adenomas and carcinomas (Am J Pathol 2004;165:1489)
Diagnostic criteria: (a) 100+ colorectal polyps, (b) germ line mutation in APC gene, (c) family history of APC and (d) at least one epidermoid cyst, osteoma or desmoid tumor


Hereditary colorectal cancer syndromes

Case reports

● Cancer in 11 and 12 year old brothers (Eur J Pediatr 2005;164:306)


● Prophylactic colectomy by age 20-25 years, must monitor rectal stump (if preserved) and possibly upper GI tract
● Screening of relatives

Gross description

● Small to large adenomas involve entire bowel
● May be flat or depressed (Int J Surg Pathol 2006;14:133)

Gross images

Extensive polyposis #1

#2, #3

Micro description

● Tubular adenomas that progress to carcinoma
● Adenomatous epithelium may be present in only a single crypt taken from flat, endoscopically unremarkable mucosa

Micro images

Familial polyposis

Additional references

eMedicine, OMIM 175100, Am J Gastroenterol 2006;101:385

End of Colon tumor > Familial polyposis syndromes of colon > Familial adenomatous polyposis of colon-classic

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