Solitary malignant Schwannoma: clinical aspects, immunohistochemistry and ultrastructure

Solitary malignant Schwannoma is a rare tumor derived from cells of the nerve sheath, the Schwann cells. During the past 6 years we have treated six patients with this tumor, four males and two females ranging in age from 18 to 69 years. Five of them had their tumors located on the trunk, which is associated with a bad prognosis. In four of the six patients ultrastructural examination played an important role in making the diagnosis of malignant Schwannoma. Light microscopy alone is insufficient because the spindle-shaped cells growing in fascicles often closely resemble other sarcomatous tumors. Ultrastructural typical findings of Schwannomas are cytoplasmic processes, intercellular junctions and basal lamina. Surgery was the sole treatment in three patients. One patient only received chemotherapy because of disseminated disease. The other two were treated with surgery combined with radiotherapy. Four patients developed distant metastases for which chemotherapy was given, but all patients died within 3 years after their initial treatment. Only two patients are free of disease 56 and 72 months after treatment. Solitary malignant Schwannoma is a tumor with a grave prognosis, for which ultrastructural and immunohistochemical examination plays an important role in order to establish the diagnosis.