Pathologic anatomy and patterns of occurrence of hepatic neoplasms, putative preneoplastic lesions, and other idiopathic hepatic conditions in English sole (Parophrys vetulus) from Puget Sound, Washington.

A comprehensive description of the histopathologic characteristics of a spectrum of idiopathic lesions in feral English sole (Parophrys vetulus), a bottom-dwelling flatfish, from Puget Sound, Washington State, is presented. Among these lesions are unique degenerative conditions, regeneration, storage disorders, foci of hepatocellular alteration (putative preneoplastic lesions), hepatocellular and biliary neoplasms, and nonneoplastic proliferative conditions, all of which morphologically resemble the lesions induced by various hepatocarcinogens-hepatotoxins in experimental exposures of fish and/or rodents. Results from a statistical analysis of the patterns of co-occurrence of these lesions in English sole are consistent with the concept, developed from experimental studies of liver carcinogenesis in rodents, that there are morphologically identifiable steps representing progression toward hepatic neoplasms. This is the first study in which it has been possible to demonstrate a close morphological congruity between a set of idiopathic hepatic lesions in any feral population and an established series of hepatic lesions inducible in rodents by certain hepatocarcinogens under laboratory conditions. Since sediments from the habitats occupied by the fish in this study have been shown to contain multiple hepatocarcinogens, the findings strengthen cumulative evidence that English sole are useful as indicators of exposure to hepatocarcinogens in aquatic environments.