The value of epithelial membrane antigen in the diagnosis of ovarian tumors.

The value of epithelial membrane antigen (EMA) in the diagnosis of ovarian tumors was investigated using an indirect immunoperoxidase staining technique on 91 histologic sections (88 tumors and 3 normal tissues) and 39 ascitic fluid smears (28 from patients with epithelial ovarian tumors and 11 from cases of myoma uteri). The rate of positive EMA staining was highest in malignant tumors (89.2%), second highest in tumors of low malignant potential (33.3%) and lowest in benign tumors (25.0%); normal ovarian tissues were negative for EMA. Of the malignant tumors, all 48 serous cystadenocarcinomas (100%) and 18 of 26 mucinous cystadenocarcinomas (69.2%) stained positively for EMA. In serous cystadenocarcinomas, the EMA staining was mainly localized on the luminal membrane of cells in well-differentiated tumors, but appeared on the entire cell surface and cytoplasm of cells in poorly differentiated tumors. The results of EMA staining on ascitic fluid smears were almost the same as the results for the histologic sections. The intensity and the localization of EMA staining were related to the grade of malignancy in these ovarian tumors. In comparison with staining for other antigens (carcinoembryonic antigen, CA-125 and human keratin protein), EMA was found to be one of the most sensitive markers for the diagnosis of ovarian cancer.