Definitive Treatment of “Malignant” Polyps of the Colon

Abstract

There has been an unremitting rise in incidence of colonic cancer in this country with no recent improvement in cure rate. As a result the evolution of colorectal cancer has been the focus of considerable attention with an enlarging body of evidence pointing to the common neoplastic polyp as a precursor to malignancy. "Neoplastic" polyps include "adenomatous polyps," "villous adenomas" and, lately recognized, "villo-glandular polyps." Experience with endoscopic removal of over 2,000 colonic polyps (with no mortality) has introduced two questions of prime concern to the surgeon: (1) What constitutes clinical malignancy in a polyp? AND, (2) When should laparatomy supplant or follow endoscopic removal? Eight hundred and ninety-two consecutive adenomatous (tubular), villous, villoglandular (villo-tubular) and "polypoid cancer" polyps are analyzed, 855 of which have been followed for 6 months to 4 years. Support is offered to the concept that villous and tubular growth patterns are merely variants of a similar base disturbance in cell renewal. Superficial cancer (carcinoma-in-situ) occurred in 6.6% of neoplastic polyps and represents no threat if the polyp is completely removed. Only when the cancer penetrates the muscularis mucosae should it be regarded as "invasive." The term "malignant polyp" should be reserved for this form. Invasive cancer was found in 5.0% of neoplastic polyps in this series. Only in this group need the question of further surgical intervention be raised. Major considerations influencing a decision for subsequent laparotomy are polyp size and gross morphology (i.e. sessile or pedunculated), histologic type (of the polyp and of the cancer itself), adequacy of clearance between depth of invasion and plane of polyp resection, and the patient's age and general condition. These are analyzed. Twenty-five of 46 patients with "malignant polyps" were subjected to abdominal exploration: 17 showed no residual cancer, whereas 8 (5 with recognized incomplete endoscopic removal) had tumor in the bowel wall. Of the remaining 21 patients, for whom endoscopic polypectomy alone was deemed appropriate, none have shown residual or recurrent cancer on clinical and endoscopic followup. Colonoscopy appears to be a most promising approach in terms of the goals of cancer programs, offering both prophylaxis and opportunity for treatment at a favorable stage of disease.