Diagnostic value of inhibin immunoreactivity in ovarian gonadal stromal tumours and their histological mimics.

Inhibin is a heterodimeric protein hormone which appears to be a sensitive serological and immunohistochemical marker of ovarian granulosa cell tumours. The purposes of this study were to examine inhibin immunoreactivity in a wide range of gonadal stromal neoplasms and to assess its value in the differential diagnosis of problematic ovarian tumours. Inhibin immunostaining was identified in eight cases of stromal hyperthecosis, 24 adult-type granulosa cell tumours, two juvenile granulosa cell tumours, nine Sertoli cell or Sertoli-Leydig cell tumours, one gynandroblastoma, three gonadoblastomas, two cases of sex cord tumour with annular tubules, two steroid cell tumours and two sclerosing stromal tumours. Inhibin was also present in 4/6 fibrothecomas and 2/3 unclassified gonadal stromal tumours. There was no staining of neoplastic cells in any of the problematic ovarian tumours, in many of which a diagnosis of gonadal stromal tumour had been initially considered. However, inhibin was detected in reactive stromal cells in many cases. Inhibin is a sensitive immunohistochemical marker of a wide range of gonadal stromal tumours and is of value in the differential diagnosis of ovarian neoplasia.