Immunohistochemical observations on binding of monoclonal antibody to epithelial membrane antigen in epithelial tumors of the oral cavity and skin.

A total of 211 cases of benign and malignant tumors of epithelial origin were studied by the immunoperoxidase method to determine the distribution profile of epithelial membrane antigen (EMA) with the use of monoclonal antibody. Normal epithelial cells in the oral mucosa and skin were usually negative for EMA staining, as were epithelial cells in hyperplastic lesions and papillomas. Paget cells and tumor cells of Bowen's disease (carcinoma in situ) demonstrated a high incidence of EMA positivity, whereas the frequency in basal cell carcinoma was unexpectedly low. Squamous cell carcinomas revealed positive EMA staining of cytoplasmic membranes, and the antigen was also present in keratinized areas. EMA expression in squamous cell carcinoma generally showed a high incidence (85%) and was higher in keratinized lesions than in unkeratinized or less well-differentiated neoplasms. EMA distribution could be classified into two forms: one in which the cytoplasmic membranes demonstrate positivity and in which a positive cytoplasmic pattern is found in parakeratinized cells in malignant foci.