[Risk of malignant degeneration of preoperatively-classified benign large sessile rectal polyps. A comparison with...

From January 1986 to December 1995 307 patients with preoperatively as benign classified rectal polyps underwent transanal endoscopic microsurgery or transanal excision at the Hospital of General and Abdominal Surgery, Johannes Gutenberg-University Mainz. Mean polyp size was 3.9 cm in diameter. Postoperatively in 233 patients (75.9%) a benign rectal adenoma was found. In 69 patients (22.5%) with the preoperative diagnosis "benign rectal adenoma" the postoperative histologic result was a carcinoma. No residual polyps were encountered on snare excision in 5 patients (1.6%) with inconclusive evidence of surgical margin involvement. The mean size of malignant polyps was 3.4 cm and significantly below the mean size of benign polyps (4.1 cm, p = 0.009). Especially in polyps with a size to 1 cm and from 1 to 2 cm in diameter the part of malignant rectal polyps was unexpected high (8/15 polyps, 53.3%, respectively 16/37 polyps, 43.3%. Patients with preoperatively as benign classified large sessile rectal polyps had a high risk of malignancy even when polyp's size was small. Therefore in toto excision has to be done also in small polyps.