Abstract
Macroscopic and microscopie features, geographic distribution and incidence of a liver tumour in iridaceous trouts are described.
The tumour appeared first as a sporadic one in some breeding institutions of Italy and subsequently reached a high incidence rate (more than 50 per cent).
It has a hepatocellular trabecular structure with some scirrhoid patches.
Cholangiomatous and cholangio-carcinomatous areas are rare. Metastases were observed in the kidney, heart, gastric wall, and so on. No parasites and no cellular inclusions were found. Attempts to transmit the tumour to animals of the same strain by transplant of fragments or by injection of acellular extracts or by living together of affected animals with normal ones gave no results.
Genetic factors in some strains of iridaceous trouts bred in Italy may have played a role in the large diffusion of the tumour, through a high inbreeding. The traumatic lesion of the liver during the squeezing of the sexual product may represent an extrinsic factor realizing the carcinogenic potentiality through the nodular hyperplastic and regenerative processes produced by such manipulation.
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