Mixed tumors of the skin. A histological and immunohistochemical study.

Sixty-four specimens of mixed tumors of the skin were studied by conventional microscopy. Sections from all 64 specimens were stained by hematoxylin and eosin, and sections from 18 of those specimens were stained by immunoperoxidase techniques for the presence of S-100 protein, carcino-embryonic antigen (CEA), keratin, actin, vimentin, epithelial membrane antigen (EMA), and gross cystic disease fluid protein-15 (GCDFP-15). Two distinctive histopathological patterns of mixed tumors of the skin became apparent, namely, apocrine and eccrine. Mixed tumors with apocrine features are by far the most common. Immunoperoxidase techniques, in our experience, do not enable differentiation between apocrine and eccrine types of mixed tumors.