Relation between radiation-induced tissue injury and its carcinogenesis of the rat small intestine

This study was undertaken to make clear the relationships between radiation-induced tissue injury and its carcinogenesis in the rat small intestine. The abdomens of Wistar rats were irradiated locally with 1000 to 2000 rads. Approximately 2 months following irradiation, visible nodules were found in the intestines of the groups receiving irradiation. Nodule incidence was 80 to 100% in groups that received 1750 or 2000 rads, 50% in the 1500-rad groups, and 3% in the 1000-rad groups, respectively. The histology of the nodules within 70 days postirradiation, revealed adenomatous hyperplasia, including invasion of submucosa, muscle layers, and serosa of the small intestine accompanied by an area of fibrous tissue resulting from desmoplastic reaction by irradiation injury. The nodule within 140-300 days postirradiation induced advanced tissue injuried, that is, a polypoid lesion in histology and intestinal nodular adhesion in macroscopic anatomy. Running parallel with the advance of the above mentioned tissue injuries, the nodules in 3 out of 18 rat during 200-300 days postirradiation showed mucoid adenocarcinoma. (author)