LIPID RICH RHABDOMYOSARCOMA

A lipid rich rhabdomyosarcoma of the paratesticular region was studied by light microscopy, histochemistry, immunohistochemistry and electro n microscopy. The tumour was composed of primitive looking, vacuolated , and pleomorphic cells. Lipid was present in varying amounts in all c ells but was especially abundant in the vacuolated and pleomorphic cel ls. Some cells showed eosinophilic fibrillary cytoplasm but cross-stri ations were not seen. Tumour cells were positive for desmin, muscle sp ecific actin, and vimentin. A few cells were myoglobin positive. At el ectron microscopy, the presence of lipid was confirmed, while thick an d thin filaments, Z disks, lamina and glycogen were observed, thereby confirming striated muscle differentiation. Although moderate amounts of lipid can be expected in almost any tumour, lipid rich rhabdomyosar comas have received little attention. The present report provides a co mprehensively examined case of such a tumour initially presenting diag nostic difficulty because of its possible confusion with liposarcoma.