A 62-year-old woman presents to her physician for routine annual examination. She has no known family history of colon disease and is asymptomatic. Stool cards and flexible sigmoidoscopy were recommended and on flexible sigmoidoscopy a 2.4-cm polyp was noted at 35 cm. A colonoscopy was performed and additional polyps were identified in the descending colon and cecum (Figure 63-1).
Colon polyps seen on colonoscopy. (Courtesy of Michael Harper, MD.)
Colon polyps are growths that arise from the epithelial cells lining the colon.
- More than 30% of middle-aged and elderly patients are found to have adenomatous polyps on screening and based on autopsy surveys; fewer than 1% will become malignant.1 The lifetime risk of colon cancer is 5.12%.2
- Patients with an adenomatous polyp have a 30% to 50% risk for developing another adenoma and are at higher risk for colon cancer. This risk is greatest in the first 4 years after diagnosis of the first polyp, and greater if a villous adenoma or more than 3 polyps were found.
- Familial adenomatous polyposis of the colon is a rare autosomal dominant disorder. Thousands of adenomatous polyps appear in the large colon, generally by age 25 years, and colorectal cancer develops in almost all of these patients by age 40 years.1 Other hereditary polyposis syndromes include Gardner syndrome, Turcot syndrome, Peutz-Jeghers syndrome, Cowden disease, familial juvenile polyposis, and hyperplastic polyposis.3
- There are several types of colon polyps, including:
- Hyperplastic polyps—These contain increased numbers of glandular cells with decreased cytoplasmic mucus and an absence of nuclear hyperchromatism, stratification, or atypia. Traditionally thought to be benign, recent evidence suggests malignant potential particularly for right-sided polyps, especially proximal hyperplastic serrated polyps1 and those associated with hyperplastic polyposis syndrome (a familial disorder with multiple [>30] hyperplastic polyps proximal to the sigmoid colon with 2 or more >10 mm).3 The percentage of polyps reported to be in this category ranges from 12% to 90%.3,4
- Adenomatous polyps—These may be tubular, villous (papillary), or tubulovillous. In a case series of 582 patients who had a polyp removed, 81% were adenomatous, including 65.0% that were tubular, 25.8% tubulovillous, 7.2% villous adenomas, and 0.5% mixed adenomatous hyperplastic polyps; 12 (1.4%) were invasive carcinomas.4
- Adenomatous polyps may be pedunculated or sessile; cancers more frequently develop in sessile polyps.1
- Villous polyps can cause hypersecretory syndromes characterized by hypokalemia and profuse mucous discharge; these more frequently harbor carcinoma in situ or invasive carcinoma than other adenomas.3
- Nonneoplastic hamartoma (juvenile polyp)—These are benign cystic polyps with mucous-filled glands, most commonly found in male children, ages 2 to 5 years, and are often found as singular lesions, but additional polyps are found on panendoscopy in 40% to 50% of children. Juvenile polyps in adolescence may be associated with hereditary syndromes that carry malignant potential....