Inhibin is a
glycoprotein hormone produced by normal ovarian granulosa cells and testicular sertoli cells. In the ovary, it inhibits the secretion of
follicle-stimulating hormone. Patients with
granulosa cell tumors (GCT) have elevated serum levels of
inhibin and this finding has been used to detect recurrent
tumor. This study attempts to determine whether
inhibin antibody (IAB) can preferentially mark GCT and Sertoli-cell or
Sertoli-Leydig cell tumors (SCT) in
paraffin-embedded tissues and facilitate distinction of GCT from
small cell carcinoma of hypercalcemic type (SCC), SCT from Sertoliform
endometrioid carcinoma (SEC), and primitive gonadal-stromal
tumors from a variety of poorly differentiated
neoplasms. Applying microwave-enhanced immunohistochemistry, a total of 126
paraffin-embedded and microwave-enhanced archival ovarian
tumors and tissues were studied by using monoclonal IAB. The
tumors included 32 adult GCT, 7 juvenile GCT, 4 metastatic GCT, 8 SCT, 7 SCC, 6 primitive gonadal stromal
tumors (PGST), 5 fibrothecomas, 6
lipid cell
tumors (LCT), 5 extrauterine
endometrial stromal sarcomas (ESS), 5
hemangiopericytomas (HPC), 1 metastatic
malignant melanoma, 1 metastatic
malignant lymphoma, and 27 epithelial
tumors including 8 SEC, 5 mucinous
tumors, and 4 Brenner
tumors. Seven
pregnancy luteomas (nodular theca
lutein hyperplasia of pregnancy), 3 corpora lutea and 2 ovarian follicles were also studied. The intensity of immunostaining was scored from one to three and the percentage of the immunoreactive
tumor cells was determined and expressed in 10% increments. Among 32 adult GCT, 31 (97%)
tumors reacted positively with IAB. The percent of positive cells ranged from 30% to 100% (average 80%). Similarly, all four metastatic GCT, 7 juvenile GCT and 4 of 5 fibrothecomas were immunoreactive with monoclonal IAB. Seven of 8 (88%) SCT, 5 of 6 (83%) PGST, all 6 LCT, 7
pregnancy luteomas, 3 corpora lutea and the 2 ovarian follicles were also positive with IAB. The most intense positivity was observed in luteinized stromal cells regardless of
tumor type. No immunoreactivity was observed in any of the 7 SCC, 5 ESS, 5 HPC, 1 metastatic
malignant melanoma, 1 metastatic
malignant lymphoma and the epithelial component of all 27 epithelial
tumors including 8 SEC. Among the mucinous
tumors of the ovary, however, 3
tumors with luteinized stromal cells showed immunoreactivity in these cells, but no positivity was seen in the mucinous epithelium. We conclude that IAB is an excellent marker for sex cord differentiation in ovarian
tumors. It can be used effectively in the diagnosis of GCT and its distinction from
epithelial neoplasms particularly SCC. The IAB may also be helpful in differentiating LCT from epithelial
malignancies. However, it cannot be used to distinguish GCT from SCT.