Lymph node metastases from carcinomas developing in pedunculated and semipedunculated colorectal adenomas.

Intramucosal carcinomas do not metastasise, but 5% to 10% of patients with submucosal cancers show lymph node involvement. Some of these submucosal cancers occur in pedunculated or semipedunculated polyps, which are usually treated by endoscopic polypectomy. Of 214 colorectal polyps removed endoscopically at the Keio University Hospital from 1976 to 1979, six showed submucosal invasive carcinoma. All six patients were subjected to colon resection, and two were found to have lymph node metastases. Consideration of these cases and of the literature suggests that resection is necessary after endoscopic polypectomy when there is carcinoma at the cut end, massive carcinomatous invasion of the neck of the polyp, lymphatic involvement, or poorly differentiated adenocarcinoma.