Cutaneous epithelioid schwannomas: a rare variant of a benign peripheral nerve sheath tumor.

Although benign epithelioid peripheral nerve sheath tumors have been described, they are rare, and benign epithelioid schwannomas have not yet been established as a specific histologic variant. We present four cases of tumors which we believe would meet criteria to be classified as benign epithelioid schwannomas. Biopsy specimens obtained from four different patients were examined with routine and immunohistochemical staining. All the tumors were well-circumscribed lesions that were surrounded by a capsule containing EMA-positive cells. The cellular component was composed of epithelioid cells, in which there was a lack of mitotic activity. Immunohistochemical studies showed the tumor cells were S-100 protein and Leu 7 positive and HMB-45 negative. In addition, type IV collagen encircled individual cells within the tumor, indicating a continuous basal lamina. We report a group of cutaneous epithelioid schwannomas. Although the presence of such tumors is not unexpected, this diagnosis may not be initially considered because of this rare cytologic feature.