Neurofibroma in a striped mullet: histochemical and immunohistochemical study.

A case of neurofibroma is reported in a wild mullet Mugil cephalus. Macro- and microscopic features are described. The tumor arose on the head as a white-greyish firm mass protruding outwards, but covered by the epidermis. The neoplastic tissue showed well-defined borders and was encapsulated; it was predominantly composed of elongated cells, with ellipsoid, hyperchromatic nuclei and pale cytoplasm. Cells were irregularly arranged: in the context of the neoplastic proliferation, these cells were usually densely packed, sometimes forming parallel arrays, but without distinctive nuclear palisades. The diagnosis of neurofibroma is also supported by the positive immunostaining for S-100 and vimentin, as well as by the negative calretinin reaction.