Nerve-sheath myxoma (perineurial myxoma).

Seventy cases of nerve-sheath myxoma, an uncommon cutaneous neoplasm, are reported. Lesions developed most frequently on the face and upper extremities, and affected women about twice as often as men. Their average size was one centimeter. Histologically, the lesions involved the reticular dermis; many extended into the superficial portions of the subcutis. They were composed of fascicles of cells with interconnected cytoplasmic processes. The neoplastic cells were associated with variable amounts of a matrix that was rich in acid mucopolysaccharides. Mitoses were common, but evidently had no prognostic significance. Only one of 70 lesions was recurrent and no metastases are known to have occurred from any. For eight cases, immunoperoxidase staining for S-100 protein was done and all were positive. One lesion showed ultrastructural features of nerve-sheath cells, specifically perineurial cells.