Adenocarcinomas of various sites may exhibit immunoreactivity with anti-inhibin antibodies. 
The aim of this study was to investigate the immunohistochemical staining of adenocarcinomas arising primary at a variety of sites with antibodies against the alpha and beta subunits of human inhibin.  We wished to determine whether positivity in an adenocarcinoma is specific for an ovarian primary.  Seventy-eight adenocarcinomas were stained with the commercially available monoclonal antibodies R1 and E4 which react against the alpha and betaA subunits of human inhibin, respectively.  In 20 adenocarcinomas, there was positivity with R1 and 46 cases were immunoreactive with E4.  Positive staining was generally weak although there was strong reactivity with R1 in five cases and with E4 in two cases.  Positive staining with antibodies against the alpha and beta subunits of inhibin may be present in adenocarcinomas arising primary at a variety of sites.  Caution should be exercised when using anti-inhibin antibodies to distinguish between an ovarian carcinoma and a sex cord-stromal tumour.  These antibodies should always be used as part of a panel.  Positivity with anti-inhibin antibodies in an adenocarcinoma is not specific for an ovarian primary.