Immunohistochemical identification of epithelial membrane antigen in sweat gland tumors by the use of a monoclonal antibody.

A total of 78 cases of adnexal tumors of the skin were examined with the use of monoclonal antibody against epithelial membrane antigen (EMA). The EMA reaction was confined to luminal surfaces and lateral borders of sweat glands, both eccrine and apocrine, being usually absent in ductal segments. Neoplastic lesions of all the adenomatous tumours and mixed tumours of sweat glands showed specifically positive EMA staining of luminal surfaces and lateral borders of tubular, duct-like, and cystic structures. However, solid foci of those tumours were negative for EMA. Tumours of ductal origin, e.g. syringomas and poromas, exhibited positive EMA staining in their plasma membrane, although normal intact keratinocytes did not stain for EMA. Immunohistochemical distribution of EMA in skin adnexal tumours was classified into two types: one in which the luminal surfaces and lateral outer borders were positive, similar to that of the normal secretory coil, and the other in which the plasma membrane of neoplastic cells of ductal origin was positive.