Expression of epithelial membrane antigen in perineurial cells and their derivatives. An immunohistochemical study with multiple markers.

Paraffin-embedded surgical pathology specimens from skin (5) and muscle (2) biopsies, from Morton's neuromas (3), traumatic neuromas (8), schwannomas (21), neurofibromas (12), and from one perineurioma and one neurothekeoma were studied by immunoperoxidase histochemistry and antibodies against epithelial membrane antigen (EMA), Leu 7 epitopes (Leu 7), S-100 protein (S-100) and cytokeratins. Normal, reactive and neoplastic perineurial cells stain consistently for EMA, whereas Schwann cells express Leu 7 and/or S-100 positivity. None of the immunoreactive cells stained for cytokeratin. Our findings indicate that perineurial and Schwann cells can easily be distinguished by their different patterns of immunoreactivity with the above markers.