Rational management of malignant colon polyps based on long-term follow-up

We reviewed the long-term results of management of 38 patients with carcinoma in colorectal polyps. Of these, 16 patients demonstrated malignant invasion of the lamina propria but not the muscularis mucosa (group I), and 22 patients showed malignant invasion of the muscularis mucosa (group II). Primary therapy for group I patients consisted of polypectomy in 12, local excision in one, and colonic resection in three. One patient had a subsequent abdominal-perineal resection and was found to have no residual disease and no lymph node involvement. Follow-up of the group I patients showed that 11 were alive and well (mean 5.8 years) and five died of unrelated causes (mean 5.2 years). Of group II patients, 12 underwent polypectomy, six local excision, and four colectomy. Of these 22 patients, 11 underwent further operation, including nine major bowel resections and two local re-excisions. None of these 11 patients had either residual tumor or lymph node metastases. One patient died of complications after abdominal-perineal resection. Follow-up showed that 18/22 group II patients were alive and well 5 to 15 years later (mean 7.5 years); four died of unrelated causes (mean 3.2 years). We then reviewed another group of 220 patients who had undergone resection for invasive colon cancer to relate the presence or absence of lymph node metastases to the depth of malignant invasion in the bowel wall. We found that 44% of this entire group had lymph node involvement. Of 36 patients with tumor confined to the bowel wall, nodal metastases occurred in only 22%. Of eight patients with malignancy superficial to the muscularis propria, only one had nodal involvement. We conclude that colon cancer tends to progress in an orderly fashion and the risk of nodal metastases increases with the depth of invasion. Carcinoma in a polyp represents a very early stage of colon cancer. We therefore recommend polypectomy as primary treatment for pedunculated polyps containing carcinoma either superficial to or invading muscularis mucosa. If histologic review demonstrates incomplete excision, lymphatic invasion, or poor differentiation, patients with lesions invading the muscularis mucosa should undergo formal colonic resection.