Clear cell sarcoma of tendons and aponeuroses: electron microscopic findings suggesting Schwann cell differentiation.

A case of clear cell sarcoma of tendons and aponeuroses arising in the elbow of a young woman is reported. Local recurrence and lymph node metastases occurred despite radiation therapy, chemotherapy, and amputation of the right arm, and the patient died of the tumor approximately ten months after the initial diagnosis. Although melanin was not observed histologically, electron microscopic studies revealed immature melanosomes. In addition, well-developed and duplicated basement membranes, and abundant intracytoplasmic microfibrils suggested melanotic Schwann cell differentiation. On sections stained immunohistochemically, S-l00 protein was present focally. The six previously reported cases of clear cell sarcoma studied electron microscopically are reviewed.