Cutaneous glomus tumor. A comparative immunohistochemical study with pseudoangiomatous intradermal melanocytic nevi.

Glomus tumor of the skin and subcutis is an uncommon neoplasm in which the histologic features can be mimicked by other dermal lesions of diverse types. The cell of origin is thought by most to be the pericyte, which has some of the ultrastructural features of smooth muscle. We examined six glomus tumors with a panel of antibodies including the myogenic markers, muscle-specific actin (HHF-35), and desmin; all tumors were immunoreactive for muscle-specific actin, but only two expressed desmin. Half of these tumors expressed the endothelial determinant, factor VIII-related antigen. Pseudoangiomatous melanocytic nevi stimulating glomus tumors were consistently immunoreactive for S-100 protein, which was not expressed by glomus tumors.