ADENOMATOUS POLYPS (TUBULAR ADENOMAS)

• May be pedunculated; stalk usually has normal epithelium; stalks longer in left colon
• 75% of all neoplastic polyps; male: female =2:1
• 0.3-3.5 cm; most are located in the sigmoid colon and rectum, but 25-40% are found in the right colon
• Thicker mucosa with goblet cell depletion, multiple cell layers, mitoses off basal layer
• Superficial areas affected first
• Although "premalignant," few adenomatous polyps progress to cancer; risk of malignancy only 1-3%; increases with number and size (esp. if >2 cm) of polyps
• Larger lesions usually have some villous component: "villoglandular polyps" or "tubulovillous polyps"; increased risk of malignant progression
• Pseudoinvasion of the stalk distinguished from carcinoma by similarity to surface glands, presence of lamina propria between glands, lack of a desmoplastic response, hemosiderin granules, or hemorrhage