Adenocarcinomas of various sites may exhibit immunoreactivity with anti-inhibin antibodies

Aims: The aim of this study was to investigate the immunohistochemical stai ning of adenocarcinomas arising primary at a variety of sites with antibodi es against the alpha and beta subunits of human inhibin. We wished to deter mine whether positivity in an adenocarcinoma is specific for an ovarian pri mary. Methods and results: Seventy-eight adenocarcinomas were stained with the co mmercially available monoclonal antibodies R1 and E4 which react against th e alpha and beta Asubunits of human inhibin, respectively. In 20 adenocarci nomas, there was positivity with R1 and 46 cases were immunoreactive with E 4, Positive staining was generally weak although there was strong reactivit y with R1 in five cases and with E4 in two cases. Conclusions: Positive staining with antibodies against the alpha and beta s ubunits of inhibin may be present in adenocarcinomas arising primary at a v ariety of sites. Caution should be exercised when using anti-inhibin antibo dies to distinguish between an ovarian carcinoma and a sex cord-stromal tum our. These antibodies should always be used as part of a panel. Positivity with anti-inhibin antibodies in an adenocarcinoma is not specific for an ov arian primary.