Abstract

A 6-month–old cultured male Clarias gariepinus weighing 950g with a mass on the tail region was observed swimming sluggishly in a concrete pond having about one thousand fish. The weight of the fish was relatively lower than majority of the fish in the pond though they were hatched at the same time. The mass was located intramuscularly towards the tail of the fish and was composed of two nodules measuring about 1 and 1.5 cm respectively with areas of necrosis at the centre. Blood was collected in a clean bottle treated with ethelene diamine tetraacetic acid, EDTA and haematology determined. It was subsequently euthanized and the mass carefully excized and fixed in 10% buffered formal saline. The tissue sample was processed by conventional methods and sections stained with Haematoxylin and eosin. Haematological determination indicated erythrocytic pathology while histologic findings revealed haphazardly arranged neoplastic cells and well vascularized tumor tissue with larger than normal capillaries. There was also infiltration of mononuclear cells in some segments of the mass. The histological findings were comparable with that for rhabdomyosarcoma and therefore it was concluded to be a case of rhabdomyosarcoma. This is the first case of rhabdomyosarcoma in fish in Nigeria.

Key words: Cultured Clarias gariepinus, spontaneous rhabdomyosarcoma, anaemia, concrete pond.