Teleost fish granulomas: some epithelial cell characteristics in their epithelioid cells.

Abstract

On examination of transverse sections of paraffin embedded specimens from 127 fish from four genera, 16 fish were found to have granulomas in various visceral organs (Kidney, liver, peritoneal fat and spleen). The number of granulomas varied from one to 14 per fish organ. The central necrotic mass of the granuloma was positive for keratin, but the epithelioid cells were negative for cytokeratin using monoclonal antibody to human keratin. Acid fast bacteria (mycobacteria) were demonstrated in the sections of the discus (Symphysodon sp.) and neon tetra (Hyphessorbrycon innesl) fishes, but not those of grass carps (Ctenopharyngodon idella) and crucian carps (Carassius carrassius). Neither fungi, other types of bacteria, nor other agents could be demonstrated in any fish. Electron microscopic studies revealed epithelial features in epithelioid cells.