Hepatocytic differentiation in retiform Sertoli-Leydig cell tumors: Distinguishing a heterologous element from Leydig cells

Sertoli-Leydig cell tumors (SLCT) of the ovary are rare sex cord-stromal ne oplasms. A minority of SLCT are characterized by a pattern resembling that of the rete ovarii and frequently have a range of homologous and heterologo us tissues. Approximately 20 cases of SLCT have been reported to have eleva tion of serum alphafetoprotein (AFP) levels, or tissue immunoreactivity for AFP, a protein usually associated with germ cell. neoplasms, especially yo lk sac tumor. We identified hepatocytic differentiation in five cases of re tiform SLCT (RSLCT), and confirmed immunohistochemically that these cells a re hepatocytes rather than Leydig cells. Hepatocytes are positive for kerat ins (AE1/3 and Cam 5.2),AFP, and ferritin, negative for vimentin, and show weak to moderate staining for inhibin. Leydig cells are negative for kerati ns, positive for vimentin, and intensely positive for inhibin. Immunohistoc hemistry is needed to distinguish hepatocytic differentiation from Leydig c ells with certainty. Including the cases in this report, hepatocytic differ entiation has been associated with a retiform pattern in SLCT in 14 of 25 c ases (56%). The association of these two patterns appears to be characteris tic of a relatively primitive sex cord-stromal neoplasm. This is a US gover nment work. There are no restrictions on its use.