[A case of malignant epithelioid schwannoma in the triceps muscle of the arm].

A patient with malignant epithelioid schwannoma in the right triceps muscle of the arm is reported. This tumor was mainly composed of plump epithelioid cells, which showed focal necrosis and nuclear arrangement in palisades. The structures and the presence of long cytoplasmic processes, discrete basal lamina, and long spaced collagen on electron microscopic examination suggested schwannian derivation of the tumor. The tumor exhibited metastasis to the axillary lymph nodes. However, no recurrence was observed a year after surgical removal, irradiation, and chemotherapy.