Colorectal Polyps

Colorectal polyps include conventional adenomas, sessile serrated lesions, traditional serrated adenomas, hyperplastic polyps and nonneoplastic lesions.

Adenomas and selected serrated lesions are precursors of colorectal carcinoma. Management therefore requires complete removal and surveillance proportional to future cancer risk.

A malignant polyp contains adenocarcinoma invading through the muscularis mucosa into the submucosa. Intramucosal carcinoma has negligible conventional nodal metastatic potential and is managed as an advanced mucosal lesion rather than invasive colorectal cancer.

Most polyps are asymptomatic.

Larger lesions may cause occult bleeding, iron deficiency anaemia or visible rectal bleeding.

A villous rectal adenoma can rarely produce substantial mucus loss with fluid and electrolyte depletion.

High quality colonoscopy defines morphology, size and location and permits endoscopic resection.

Large nonpedunculated lesions should be assessed for deep submucosal invasion before removal. Lesions strongly suspicious for deep invasion should not undergo piecemeal resection because pathology then cannot reliably assess depth or margins.

Most benign polyps should be completely removed endoscopically.

Cold snare excision is preferred for most small lesions. Large nonpedunculated lesions are generally treated with advanced endoscopic mucosal resection or endoscopic submucosal dissection according to morphology and invasion risk.

Malignant polyp

Endoscopic resection may be definitive when an invasive cancer is removed en bloc with favourable pathology.

Features favouring formal oncological colectomy include:

• Poor differentiation
• Lymphovascular invasion
• Tumour budding
• Involved or inadequately assessable resection margin
• Deep submucosal invasion above approximately 1 mm in a nonpedunculated lesion
• Piecemeal removal preventing reliable pathological assessment.

For a pedunculated malignant polyp, tumour within 1 mm of the resection margin, poor differentiation or lymphovascular invasion indicates significant residual or nodal risk.

Surveillance

After a high quality colonoscopy with complete resection:

• One or two tubular adenomas below 10 mm: repeat colonoscopy in 7 to 10 years
• Three or four adenomas below 10 mm: 3 to 5 years
• Five to ten adenomas: 3 years
• Adenoma at least 10 mm, villous histology or high grade dysplasia: 3 years
• More than ten adenomas: approximately 1 year, with consideration of an inherited polyposis syndrome
• Piecemeal resection of a lesion above 20 mm: first surveillance at approximately 6 months.