Immunohistochemical study of testicular sex cord-stromal tumors, including staining with anti-inhibin antibody.

Inhibin is a peptide hormone produced by ovarian granulosa cells and testicular Sertoli cells. Ovarian granulosa cell and other sex cord-stromal tumors usually exhibit positive immunohistochemical staining with antiinhibin antibodies, and this may be valuable in differentiating these neoplasms from histologic mimics. In the present study, we investigated the immunohistochemical staining of testicular sex cord-stromal tumors using antiinhibin. Immunostaining with CAM5.2, vimentin, S-100 protein, desmin, epithelial membrane antigen (EMA), carcinoembryonic antigen (CEA), and placental alkaline phosphatase (PLAP) also was performed because few studies have investigated in detail the immunophenotype of testicular sex cord-stromal tumors. Fifteen of 16 Leydig cell tumors exhibited strong positive staining with antiinhibin. A proportion of Leydig cell tumors also stained positively with CAM5.2 (7 of 16), vimentin (14 of 16), S-100 protein (10 of 16), desmin (2 of 16) and epithelial membrane antigen (4 of 16). Four of six testicular sex cord-stromal tumors with varying degrees of Sertoli or granulosa cell differentiation were positive with antiinhibin, as were two of three sex cord-stromal tumors that were unclassified. Some of these tumors were positive with CAM 5.2, vimentin, S-100 protein, desmin, and epithelial membrane antigen. All tumors were negative with carcinoembryonic antigen and placental alkaline phosphatase. The immunohistochemical findings show that, analogous to their ovarian counterparts, most testicular sex cord-stromal tumors are immunoreactive with antiinhibin. Immunohistochemistry using this antibody as part of a panel may be valuable in confirming a diagnosis of testicular sex cord-stromal tumor and in differentiating these neoplasms from others that may mimic them.