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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
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● 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

Diagrams
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Hereditary colorectal cancer syndromes

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

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

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

Gross images
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Extensive polyposis #1

#2, #3

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

Micro images
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Familial polyposis

Additional references
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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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