Pathology of hepatomas and other liver abnormalities in English sole (Parophrys vetulus) from the Duwamish River estuary, Seattle, Washington.

Liver abnormalities were found, by gross and histopathologic examination, in 92% of the English sole (Parophrys vetulus) from the Duwamish River Estuary, Seattle, Washington. Hepatomas were found in 32% (20 of 62) of the English sole. Other observed liver aberrations included increased fatty vacuolation, congestion, structure disarray, increased size and number of melanin-macrophage centers, centrolobular fatty degeneration and necrosis, increased amounts of perivascular connective tissue, intercellular melanin deposits, and hepatocellular hypertrophy often associated with the presence of bizarre nuclei and/or multiple nucleoli. Livers evidencing microscopic lesions were usually discolored. Livers containing hepatomas were often mottled yellow or tan and brown; occasionally, hepatomas were visible as tan or white nodules. Although the cause(s) of the liver abnormalities has not been conclusively identified, chemical analyses of Duwamish River English sole have detected polychlorinated biphenyl (PCB) levels of about 1.5 ppm (dry wt) in total body tissue. Many of the above-mentioned abnormalities, with the exception of hepatomas, have been observed in fish exposed to PCB's.