Abstract

During the past 20 yr, 17 colorectal carcinomas (0.47%) were incidentally detected among 3,638 autopsied patients without clinically evident colorectal carcinoma, including 2,232 males and 1,406 females, more than 40 yr old. Among the 15 male and two female index subjects, six (0.33%) were detected in the first and 11 (0.60%) in the second decade. During their survival periods, fecal occult blood studies were performed in 14 cases and positive in 12 (86%); however, two of them had gastric ulcers which were responsible for the occult blood. During the recent 11 yr, six cases (0.48%) of colorectal carcinoma (four of them males; two, females) also were detected among 1,249 inpatients who were examined by barium enema and/or colonoscopy, including 816 males and 433 females, 40 yr old, or more, in the Department of Radiology. Fecal occult blood was detected in four cases (67%) before colonic investigation. Compared with 708 surgically resected carcinomas, the incidental lesions from both sources were smaller, consisted of higher percentages of Dukes' A type, and arose predominantly from the sigmoid colon and, rarely, from the rectum. These results indicate that the prevalence of colorectal carcinoma and its predominance in the sigmoid colon have not only apparently but actually increased in Japan, apart from improved diagnostic capabilities, and that false-negative rates with occult blood tests were surprisingly low in these autopsied cases and inpatients.