Benign tumors of the digestive tract among atomic bomb survivors, 1961-1970 Hiroshima.

The occurrence of benign tumors and diverticular of the digestive tract was investigated in an autopsy study of a fixed population of 100,000 samples in Hiroshima and Nagasaki. There were 664 benign tumors and 40 diveritcula. Polyps were the most frequent tumor, were found more often in older people, occurred as single pedunculated well-differentiated adenomatous tumors, and most were less than 5 mm in greatest dimension. Larger polyps tended to have more atypism, but none showed definite premalignant change. No transition from benign to malignant polyps was seen. Polyps were found most frequently in the large intestine and in a large number (21%) and, when cancer of the large intestine was present, benign polyps were also found. Far more polyps are found when special intensive search is made for them. Comparison of the occurrence of benign polyps in different geographic areas must be adjusted for age and method of search as well as for other features such as histological type, dysplasia, etc. There was no evidence that the occurrence of benign tumors or diveritcula was related to prior exposure to ionizing radiation.