An epidermal papilloma of the Atlantic samon II: Ultrastructure and etiology.

Ultrastructure of the Atlantic salmon papilloma was studied, and virus isolation was attempted. The papilloma cells were similar to normal epidermis in having interdigitating cell membranes with desmosomes. The nuclei, however, were more regular in shape than normal epidermal nuclei and the chromatin tended to be marginated and clumped. No cytopathic viral agents were isolated.