Papillomatous Growth of Skin in Japanese Common Goby, Acanthogobius flavimanus

Abstract

A spontaneous hyperplastic growth of skin which developed in Acanthogobius flavimanus collected from the Mikawa-bay area was studied preliminary from the view point of histopathology and virology.
The hyperplastic region showed proliferating epidermal cells accompanied with relativelythin connective tissues. The lesions were characterized by giant cells which were observed among the hyperplastic epidermal cell layers.
However, in the hyperplastic lesions less than 1mm thick, possibly in the early stage of the disease, the growth was characterized by angiomatous or fibrous connective tissues.In these connective cell layers, histiocytic or round cells were frequently observed. Even when the epidermal layer did not show too extensive proliferative growth, the basal cells changed their morphology and lost their cylindrical cell natures.
Similar changes of the epithelial and connective tissue cells usually occurred in the transitional area between the normal skin and the papillomatous growth. Infiltrative growth of the hyperplastic epithelial cell elements into adjacent normal skin or muscular layer was not observed in any cases.
The findings closely resembling the morphology of this disease entity have been reported in papillomatous growth of skin in flat fishes. Considering the different charcteristics of epidermis between mammal and fish, the disease of the goby was considered as one of a unique neoplastic disease found in fishes.
Factors possibly related to the development of the papillomatous growth were also discussed in this communication.