Gross and histopathological characteristics of two lipomas and a neurofibrosarcoma detected in aquacultured southern bluefin tuna, Thunnus maccoyii (Castelnau), in South Australia

Abstract Three visible lesions were examined from two specimens of southern bluefin tuna. The lesions were examined grossly and two were identified as lipomas, the third bore similarities to a schwannoma. Histopathology confirmed that two consisted of mature adipocytes consistent with a diagnosis of lipoma. The third lesion consisted of spindle cells in Antoni A and B patterns and was tentatively diagnosed as a malignant schwannoma. Immunohistochemistry identified both S100 and glial fibrillary acid protein expression within the lesion, which, together with the histopathological appearance, is consistent with a diagnosis of neurofibrosarcoma. Keywords: immunohistochemistry, lipoma, neoplasm, neurofibrosarcoma, schwannoma, tuna.