Hepatic neoplasms in wild common carp

Common carp Cyprinus carpio from West Point Lake, Georgia-Alabama, were sampled (N = 81) during fall 1991. Gross examination revealed single nodules in the livers of four fish; representative tissues from all sampled fish were preserved for histological examination. One of the four nodules was a hepatocellular adenoma and the other three were hepatocellular carcinomas. Two additional neoplasms, a cholangioma and a cholangiocellular carcinoma, were found in one of the nodule-containing livers. Nonneoplastic liver changes that were found microscopically included nuclear pleomorphism, hepatic megalocytosis, and occurrence of clear cell foci. Possible predisposing factors, including exposure to polycyclic aromatic hydrocarbons, are discussed. These are the first reported cases of hepatic neoplasms in common carp, a species generally considered resistant to hepatocellular neoplasia.