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Case 78: Colonic polyp

You discover this lesion whilst performing a colonoscopy for iron deficiency anaemia in a 70 year old woman. The lesion is located in the sigmoid colon.

1. What is the likely pathology?

This is a large pedunculated polyp. It is most likely to be a tubular adenoma.

2. How would you manage this lesion?

Perform snare polypectomy and retrieve the polyp for histologic examination. The remaider of the colon should be examined for synchonous lesions. A large polyp like this could be excised on the way out after complete colonoscopy after noting its location.

3. If histologic examination revealed evidence of invasive carcinoma what would you do?

The extent of invasive carcinoma and completeness of excision need to be assessed to determine the risk of lymph node metastases. Low risk lesions that have been completely excised simply require early repeat colonoscopy (within 12 months) whereas high risk lesions require formal colectomy to ensure complete excision and lymph node dissection.

The risk associated with a malignant polyp is measured according to Haggitt's classification. There are 5 levels of invasion recognised in pedunculated polyps.
Level 0: not invasive carcinoma
Level 1: invasion to the head of the pedunculated polyp
Level 2: invasion to the neck of the pedunculated polyp
Level 3: invasion to the stalk of the pedunculated polyp
Level 4: invasion to the base of the pedunculated polyp
All sessile lesions are level 4.

In addition to the Haggitt classification the invasive carcinoma must be low grade and with no evidence of lymphovascular invasion for colonoscopic polypectomy to be considered adequate.



Suggested reading: Nivatvongs, S. "Surgical Management of Early Colorectal Cancer" World J. Surg. 24, 10521055, 2000