Abstract
The authors histopathologically examined melanoma found on the head of a three-year-old rainbow trout(Salmo gairdneri)caught in Samegai Trout Culture Station in 1974. A neoplastic mass was observed to be a protuberance of black color with papillate surface.
Histopathologically, the tumor arose from the dermal loose connective tissue. It consisted of a considerable number of mature melanocytes and immature ones extending in all directions as a parenchyma and of a large amount of thin collagenous fibers as a stroma.
Metastatic production was not observed in this case.
