Diethylnitrosamine-induced pancreatic neoplasms in the fish Rivulus ocellatus marmoratus.

Diethylnitrosamine [(DEN) CAS: 55-18-5] caused neoplasms of the exocrine pancreas in rivulus, Rivulus ocellatus marmoratus, a self-fertilizing hermaphroditic fish, after a single exposure to 810, 270, or 130 mg DEN/liter or after a continuous exposure to 50, 17, or 9 mg DEN/liter. Rivulus developed pancreatic adenomas after a single exposure. After continuous exposure, pancreatic adenomas, cystadenomas, and adenocarcinomas developed. Adenocarcinoma developed in fish first exposed as larvae but not in those first exposed as juveniles. Adenocarcinoma of pancreatic or biliary origin invaded the intestinal muscularis layer and mucosa. Dedifferentiation of acinar cells preceded the formation of adenomas, and atypical acinar cells formed parts of some of the ductlike structures in the pancreatic neoplasms.