Leydig Cell Tumor : Inhibin
Immunohistochemistry of Leydig Cell Tumors (LCT): LCT are positive for inhibin-alpha, calretinin, melan-A (MART1) and CD99. Immunostain for steroidogenic factor 1 (SF1) is a highly sensitive marker for sex cord-stromal tumors as a group. There is variable positivity for cytokeratin, synaptophysin, and chromogranin. S-100 protein is positive in < 10% of cases. Beta-catenin is negative. Rare cases are positive for PLAP. p53 is more likely to be positive in malignant cases.
Inhibin-alpha (shown here) is a sensitive and a specific marker that serves to separate testicular sex cord-stromal tumors (inhibin-pos) from germ cell tumors (inhibin-neg). In one immunohistochemical study, Inhibin-alpha expression was seen in 91% of sertoli cell tumors and 100% of sertoli cell adenomas and leydig cell tumors (Iczkowski KA et al. Mod Pathol 1998 Aug; 11(8):774-9)