Metastatic malignant mixed tumor of the skin. Ultrastructural and immunocytochemical characterization, histogenetic considerations and comparison with benign mixed tumors of skin and salivary glands.

Malignant mixed tumors of the skin (chondroid syringoma) are exceedingly rare. Few reports can be found in the literature and there are only two published cases in which electron microscopy has been performed. The precise histogenesis of this neoplasm is still disputed and the nature and mechanism of secretion of the intercellular substance is unknown as yet. Some authors believe that in mixed tumors of salivary glands this material could be produced by myoepithelial cells. A case is reported in which ultrastructural and immunocytochemical studies were performed in an effort to elucidate the histogenesis of malignant mixed tumors of skin and their relationship to other benign mixed tumors of the skin and salivary glands. The new information that has been obtained is interpreted in light of the findings provided by all published reports of malignant mixed tumors of the skin.