Tumor markers in the human ovary and its neoplasms. A comparative immunohistochemical study

The incidence and histologic characteristics of the expression of placental alkaline phosphatase (PLAP) in ovarian tumors was compared with that of five other tumor antigens. Three monoclonal antibodies were used for the specific localization of PLAP. PLAP was present in some sex cord cells of the 13-16-week fetal ovary, probably germ cells. In normal ovaries, all antigens except carcinoembryonic antigen (CEA) were frequently found in inclusion cysts; the germinal epithelium was positive only for cancer antigen 125 (CA 125). The frequency and extent of PLAP expression in nonmucinous carcinomas was higher than observed for CA 19-9 and CEA, but was lower than for CA 125 and human milk fat globule antigen. Serous tumors had the highest PLAP expression, followed by endometrioid and poorly differentiated adenocarcinomas, and some other tumors. PLAP was predominantly membranous; its histologic distribution was in general heterogeneous. Different antibodies to PLAP gave different staining intensities in some tumors, but the staining patterns were always qualitatively identical.