Purely epithelioid schwannoma. Two case reports and a review of the literature.

The authors describe 2 cases of purely epithelioid schwannomas, one spinal the other peripheral. At surgery, the spinal schwannoma appeared as an orange-sized, solid, brown mass. Total removal of the tumor was performed. The peripheral schwannoma appeared as a fusiform, brown, movable mass in the sensitive branch of the left tibial nerve and was removed by a wide en bloc excision. Intraoperative nerve action potentials were performed both prior to and following excision of the lesion. Histologically, the tumors were composed of round or polygonal cells arranged in necrotic clusters and anastomosing cords. There were areas of spindle cells. The epithelioid cells were round to oval with abundant cytoplasm. Mitoses were frequent (3 out of 10 in high-power field). S100 protein immunoreactivity was present diffusely in tumor cells (both nuclear and cytoplasmic), whereas cytokeratin, NSE, and anti-melanoma reactions gave negative results. After a long follow-up, the neurological condition of the patients is excellent and there are no signs of either recurrence or metastasis. The therapeutic management of epithelioid schwannoma is discussed.