Adenomatous polyps of the colon

Adenomatous polyps are the most common colonic neoplasm, 70% of which are within the reach of the sigmoidoscope. About 75% of adenomatous polyps occur in the rectum and sigmoid colon. This distribution of lesions is paralleled by the distribution of colonic carcinoma and supports the possible development of carcinoma from pre-existing polyps.

There are three histological types:

• tubular adenomas
• villous adenomas
• tubulo-villous adenomas

They may present with bleeding, prolapse and rarely intussusception, but most commonly they are asymptomatic.

Colonic polypectomy has simplified the management of this condition.

Malignant potential is determined by:

• size - 1% risk of adenocarcinoma if less than 1 cm in diameter; 10-50% risk if greater than 2 cm
• histologic type - greatest malignant potential for villous adenoma; least for tubular
• degree of epithelial dysplasia - increasing dysplasia associated with increasing risk of invasive carcinoma
• number of lesions