Malignant epithelioid schwannoma of the skin. A low-grade neurotropic malignant melanoma?

We studied a polypoid cutaneous neoplasm excised from the left arm of a 23-year-old man by light microscopy, immunohistochemistry, and electron microscopy. Histologically, the tumor was composed of a proliferation of round to oval epithelioid cells that were arranged in fascicles and showed a prominent perineural distribution. Immunohistochemistry revealed the presence of S-100 protein and vimentin within tumor cells. Electron microscopy demonstrated reduplication of basal lamina and abundant long-spacing collagen in intercellular spaces. The findings are consistent with a primary malignant epithelioid schwannoma of the skin. We discuss the relationship of this lesion with other neoplasms in the spectrum of tumors showing schwannian and melanocytic lines of differentiation.