Tubular Adenomas

Present in ∼30% of adults; pedunculated or sessile; usually asymptomatic; ∼5% cause occult blood in stool; may cause obstruction; overall risk of malignant degeneration correlates with size (<2% if <1.5 cm in diameter; >10% if >2.5 cm in diameter) and is higher in sessile polyps; 65% found in rectosigmoid colon; diagnosis by barium enema, sigmoidoscopy, or colonoscopy. Treatment: Full colonoscopy to detect synchronous lesions (present in 30%); endoscopic resection (surgery if polyp large or inaccessible by colonoscopy); follow-up surveillance by colonoscopy every 2-3 years.

Villous Adenomas

Generally larger than tubular adenomas at diagnosis; often sessile; high risk of malignancy (up to 30% when >2 cm); more prevalent in left colon; occasionally associated with potassium-rich secretory diarrhea. Treatment: As for tubular adenomas.

Hyperplastic Polyps

Asymptomatic; usually incidental finding at colonoscopy; rarely >5 mm; no malignant potential. No treatment required.

Hereditary Polyposis Syndromes

See Table 72-2 Hereditable (Autosomal Dominant) Gastrointestinal Polyposis Syndromes.

1. Familial polyposis coli (FPC): Diffuse pancolonic adenomatous polyposis (up to several thousand polyps); autosomal dominant inheritance associated with deletion in adenomatous polyposis coli (APC) gene on chromosome 5; colon carcinoma from malignant degeneration of polyp in 100% by age 40. Treatment: Prophylactic total colectomy or subtotal colectomy with ileoproctostomy before age 30; subtotal resection avoids ileostomy but necessitates frequent proctoscopic surveillance; periodic colonoscopic or annual radiologic screening of siblings and offspring of pts with FPC until age 35; sulindac and other nonsteroidal anti-inflammatory drugs (NSAIDs) cause regression of polyps and inhibit their development.
2. Gardner's syndrome: Variant of FPC with associated soft tissue tumors (epidermoid cysts, osteomas, lipomas, fibromas, desmoids); higher incidence of gastroduodenal polyps, ampullary adenocarcinoma. Treatment: As for FPC; surveillance for small-bowel disease with fecal occult blood testing after colectomy.
3. MYH-associated polyposis: Rare autosomal recessive syndrome due to biallelic mutation of MUT4H. Treatment: Biennial surveillance colonoscopy starting at age 25-30.
4. Turcot's syndrome: Rare variant of FPC with associated malignant brain tumors. Treatment: As for FPC.
5. Nonpolyposis syndrome: Familial syndrome with up to 50% risk of colon carcinoma; peak incidence in fifth decade; associated with multiple primary cancers (esp. endometrial); autosomal dominant; due to defective DNA mismatch repair.
6. Juvenile polyposis: Multiple benign colonic and small-bowel hamartomas; intestinal bleeding common. Other symptoms: abdominal pain, diarrhea; occasional intussusception. Rarely recur after excision; low risk of colon cancer from malignant degeneration of interspersed adenomatous polyps. Prophylactic colectomy controversial.
7. Peutz-Jeghers syndrome: Numerous hamartomatous polyps of entire GI tract, though denser in small bowel than colon; GI bleeding common; somewhat increased risk for the development of cancer at GI and non-GI sites. Prophylactic surgery not recommended.