The site of inhibin production in ovarian neoplasms.

Inhibin, a physiological product of ovarian follicle cells, normally absent in serum of postmenopausal women, is elevated in adult granulosa cell tumours of the ovary. Recently, high serum levels of inhibin were reported in carcinomas and, surprisingly, also in Krukenberg tumours of the ovary. This study attempted to determine the site of inhibin production in primary (111 cases), metastatic (13) and secondary (10) ovarian tumours by using immunohistochemistry. Positive staining in tumour cells was encountered in all cases of sex-cord- stromal cell tumours, adult (13) and juvenile (3) granulosa cell tumours, thecofibromas (10), in a lipid cell tumour (1) and a Sertoli-Leydig cell tumour (1). Primary and secondary tumours not derived from sex-cord stroma revealed no positivity in tumour cells, but in theca-like cells in the surrounding non-neoplastic ovarian stroma. A positive reaction was not observed in non-tumour-bearing ovaries of a control group. The ovarian inhibin of postmenopausal women is derived from activated sex-cord stroma or sex-cord-stromal neoplasms. Therefore, elevated serum inhibin concentrations in women with primary or secondary ovarian neoplasms with other histogenesis seem to be due to an activation of the non-neoplastic ovarian stroma. Inhibin will fail to be a tumour marker in these cases. By contrast, it will be useful in proving sex-cord differentiation by immunohistochemistry and might be used in surveillance of malignant sex-cord derived neoplasms by serum assays.