Immunoexpression of Inhibin α Subunit, Inhibin/Activin βA Subunit and CD99 in Ovarian Tumors

Abstract

Abstract Objective.—Anti–inhibin α and inhibin/activin βA subunit and anti-CD99 monoclonal antibodies (mAbs) have recently been demonstrated to be able to label ovarian granulosa cells; thus, they may be of value in the diagnosis of granulosa cell tumors. The present study aimed to determine what combination of these mAbs may be useful for the differential diagnosis of sex cord–stromal tumors of ovary. Design.—Immunohistochemical analyses with anti–inhibin α and inhibin/activin βA subunit antibody and anti-CD99 mAb were performed on 42 ovarian tumors, including sex cord–stromal tumors (29), ovarian epithelial cancers (10), and Krukenberg tumors (3). Results.—All sex cord–stromal tumors were positive for inhibin α subunit, and 17 cases (58.6%) of sex cord–stromal tumors were immunoreactive for inhibin/activin βA subunit. Epithelial tumors and Krukenberg tumors were all negative for inhibin/activin βA subunit except mucinous carcinoma, which showed strong cytoplasmic immunoreactivity. All sex cord–stromal tumors except one granulosa cell tumor showed membranous staining for CD99. A case of serous carcinoma and a case of mucinous carcinoma were positive for CD99, and the remaining epithelial tumors and Krukenberg tumor were all negative for CD99. Conclusions.—The results of immunohistochemical analysis, together with literature review, suggest that inhibin α subunit may be a useful diagnostic marker for sex cord–stromal tumor of the ovary. In addition, anti-CD99 antibody may be useful for the differential diagnosis between ovarian tumors. Inhibin/activin βA subunit has a limited usefulness in the differential diagnosis of ovarian tumor because of its wider immunoreactivity for both sex cord–stromal tumors and mucinous carcinomas. The differential diagnosis of sex cord–stromal tumors of the ovary would be better made with a combined use of both anti–inhibin α subunit and anti-CD99 mAbs.