Is a biopsy necessary for colon polyps suitable for polypectomy when performing a colonoscopy?

Background: The incidence of colorectal cancer is increasing in Taiwan. Adenomatous polyps are known to be precancerous lesions and need to be removed. New techniques like chromendoscopy, magnifying endoscopy, narrow band imaging and magnifying endoscopy with flexible spectral imaging color enhancement may improve the accuracy of identifying precancerous polyps but are not widely available in the real world. This study analyzed the conventional biopsy method in diagnosing early colon cancer and the necessity for subsequent surgery after polypectomy.

Methods: From January 2002 to December 2007, 1027 adenomatous polypoid specimens taken from 720 patients who received polypectomy by conventional white light colonoscopy were studied. The pathologic reports of 26 specimens of early cancer or high grade dysplasia from 25 patients were analyzed. Protruding polyps were classified as pedunculated (o-Ip), subpedunculated (o-Isp) and sessile (o-Is).

Results: Fourteen of the 26 specimens were type o-Ip, 10 were type o-Isp, and 2 were type o-Is. The pathologic reports were high grade dysplasia (n = 5), mucosal adenocarcinoma (n = 18) and submucosal adenocarcinoma (n = 3). Among these, 7 lesions from 7 patients received a randomized biopsy instead of immediate polypectomy. Adenoma was reported in 6 of them with only one malignancy detected (false negative rate: 86%). Eight patients received surgery. The mean follow-up period for these patients was 17 months, and none of them had recurrences.

Conclusions: The randomized biopsy method for adenomatous polyps has a high false negative rate for early colon cancer and high grade dysplasia and is therefore not necessary in cases of protruding type polyps which can be removed by polypectomy. An adequate direct polypectomy may completely remove the protruding type of early colon cancer.