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Liver histopathology of flounder (Platichthys flesus) in Dutch coastal and estuarine waters, with particular reference to neoplastic disease and their relationship with environmental factors

Histopathologische veranderingen, in het bijzonder nieuwvormingen, in de lever van de bot (Platichthys flesus) uit Nederlandse kustwateren en estuarien, en de relatie met milieufactoren

Synopsis

This paper reports the detailed histopathological analysis of livers of flounder (Platichthys flesus) sampled in Dutch coastal and estuarine waters during 1985-89. In conjunction with an epidemiological study of grossly identifiable diseases at 10 sampling locations, 210 livers showing gross nodular lesions (diameter > 2 mm) and 315 livers showing no gross pathology were collected. Of the 210 livers with grossly observable nodules, 67% were diagnosed as having neoplasia. The majority of these neoplasms were identified as hepatocellular adenoma ; 13.1% were diagnosed as hepatocellular carcinoma. Most of the remaining modules were diagnosed as foci of cellular alteration, which are considered to be pre-neoplastic lesions. Routine histopathological examination of livers showing no gross pathology resulted in the identification of a range of lesions including hepatocellular adenoma, foci of cellular alteration, inflammatory lesions, focal necrosis, regenerative foci, hydropic vacuolated lesions of bile duct cells and hepatocytes, and fibrillar hepatocytes of unknown significance. In addition, indices were used to quantify the presence of storage vacuoles (glycogen and lipid) and the density of melanomacrophage centres. The results indicate that a small proportion of neoplasms would be missed if only livers with grossly detectable nodules were subjected to histological examination. The prevalence of foci of cellular alteration at the different sampling sites showed a good correspondence with that of neoplasia, providing support for the hypothesis that these conditions represent stages of the same process. Of the other lesions and quantitative indices, only bile duct vacuolization had a spatial distribution similar to that of neoplasia. The findings indicate that the occurrence of liver neoplasms in flounder represents a promising tool for monitoring exposure to potential carcinogens. However, because of the long latency period associated with tumour development, there will be a need to identify early markers preceding tumour formation (including possibly fca). This will be subject of future laboratory studies.
 

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