Immunohistochemical study of 3 beta-hydroxysteroid dehydrogenase in sex cord-stromal tumors of the ovary.

3 beta-Hydroxysteroid dehydrogenase (3 beta-HSD), which converts pregnenolone to progesterone, was localized immunohistochemically in 18 thecomas, 23 fibromas, 5 granulosa-cell tumors, 5 sclerosing stromal tumors, and 2 steroid-cell tumors. Immunohistochemical study of estrogen, progesterone, and testosterone was also performed in serial sections of thecomas and fibromas. In thecomas, immunoreactivity of 3 beta-HSD was observed only in luteinized theca cells and thecomatous tumor cells with abundant pale to vacuolated cytoplasm but not in spindled tumor cells and thecomatous tumor cells with small to moderate amounts of pale to vacuolated cytoplasm. Immunoreactivity of steroids was not observed in thecomas except for testosterone immunoreactivity in one case. No immunoreactivity of steroids or the enzyme was present in fibromas. No tumor cells were positive for 3 beta-HSD in any of the cases of granulosa-cell tumor examined. Immunoreactivity of 3 beta-HSD was present in cells in steroid-cell tumors and polygonal tumor cells with prominent cytoplasmic vacuoles in two cases of sclerosing stromal tumor. Thus, 3 beta-HSD can be a good immunohistochemical marker of steroidogenesis in functioning ovarian neoplasms.