Epithelioid Malignant Schwannoma

A case of epithelioid malignant schwannoma (EMS) is reported. The tumor arose in the left radial nerve at the axillary fossa of a 65-year old male. A few months after resection of the primary axillary tumor, several intrapulmonary metastases appeared. Microscopically, the primary tumor showed highly cellular areas of polygonal or rounded cells, resembling lymphoma or melanoma, while the metastatic tumors revealed cord formation or rows, resembling carcinoma. Immunohistochemical studies showed that some of these tumor cells contained S-100 protein. Ultrastructurally, these tumor cells revealed delicate cytoplasmic projections, which contained bundles of microfilaments. However, the tumor cells did not have melanosomes. Varying amounts of basal lamina material surrounded the tumor cells. From the above features, we obtained a correct diagnosis of EMS. Acta Pathol. Jpn. 32: 195∼202, 1989.