It is obviously desirable to obtain information about the life history of colo-rectal polyps and the time for an adenoma to become malignant. Direct observations are very few because the natural history of them is usually interrupted by surgical treatment or endoscopic polypectomy.
Seven patients with polyp at the sigmoid colon were repeatedly examined radiologi-cally. In case 1, a diagnosis of cancer was made four years and 11 months after the detection of a clinical polyp at the same site. Volume doubling time (tD) of carcinoma was 344.8 days. In case 2, a polyp (tubular adenoma) grew quickly and volume doubling time were 213.4 days. In case 3, a polyp grew quickly during the first 12 months (volume doubling time was 225.9 days), then it stopped growing. In case 4-7, polyps did not grow during the follow-up observation for 14-27 months.
Therefore, it is interesting that some tubular adenomas grow quickly, while others grow slowly.