Spindle cell epithelioma, the so-called mixed tumor of the vagina. A clinicopathologic, immunohistochemical, and ultrastructural analysis of 28 cases.

A total of 28 examples of vaginal mixed tumors, a circumscribed tumor composed predominantly of spindle cells, but often admixed with minor glandular, and focal areas of squamous differentiation along with localized hyaline globules, were evaluated. In addition to the clinicopathologic correlation with light microscopy, 10 cases were analyzed immunohistochemically by a panel of antibodies for keratin, smooth muscle actin, S-100 protein, and glial fibrillary acidic protein; five cases were also evaluated for estrogen and progesterone receptors. Ultrastructural analysis was performed on two tumors. The results indicate an epithelial differentiation in the predominating spindle cells based upon an intense immunoreaction with cytokeratin in nine of 10 cases and the presence of tonofilaments and desmosomes at the ultrastructural level. Contrary to mixed tumors of salivary gland and breast origin, no evidence of a myoepithelial differentiation was identified in these tumors. The name vaginal spindle cell epithelioma is proposed for these neoplasms as being more descriptive of the true nature of these tumors.