[Malignant peripheral nerve sheath tumor with rhabdomyoblastic differentiation and glandular component]

An exceptional case of malignant peripheral nerve sheath tumor with striated muscle differentiation and glandular component is reported, in a 52-year old man. This tumor measured 8 cm in diameter, and was localized in the chest wall, infiltrating the skeletal muscle. The mesenchymal portion of the tumor was composed mostly of spindle cells arranged in interlacing fascicles. Between these fascicles, there were large cells with abundant eosinophilic cytoplasm and clear elongated nucleus. Immunohistochemical study demonstrated cytokeratin, EMA and CEA expression in the glandular component and S100 protein expression in the major portion of the mesenchymal component. The large cells identified as rhabdomyoblasts, expressed desmin, myoglobin, alpha-SR actin and alpha-SM actin. The tumor recurred 5 years after its resection. Histological and immunohistochemical features were identical. We think that positivity of neoplastic striated muscle cells with alpha-SM actin reflects an early differentiation phase of these cells.