Colorectal villous and tubulovillous adenomas equal to or greater than four centimeters.

The records of 237 patients treated for benign and malignant villous and tubulovillous adenomas at Roswell Park Memorial Institute from 1963 to 1987 were reviewed. Sixty-five adenomas were greater than or equal to 4 cm and form the basis of this report. Fifteen (23%) were in the cecum, 3 (5%) in the right colon, 1 (1%) in the splenic flexure, 10 (15%) in the sigmoid colon, and 36 (55%) in the rectum. The most common symptoms were rectal bleeding (70%), mucus diarrhea (44%), constipation (22%), and tenesmus (19%). Fifty-five (85%) of these large adenomas contained invasive adenocarcinoma and one in situ carcinoma. Two thirds of invasive carcinomas arose from predominantly villous adenomas and one third from tubulovillous adenomas. Half of all malignant adenomas demonstrated metastases to regional lymph nodes or distant metastases. Seven malignant adenomas (12%) were associated with synchronous adenocarcinomas of the colon, and 29% of malignant adenomas were associated with synchronous adenomatous polyps, principally tubular type. Four of nine benign, large adenomas were associated with synchronous adenomas but with no adenocarcinomas. No relationship was found between the size of the adenoma, location, or Dukes' stage. Though the incidence of in situ and invasive carcinomas is clearly related to the size of the adenoma, a linear relationship could not be demonstrated.