Selected immunohistochemical markers can also be helpful to distinguish the different germ cell-tumor elements: dysgerminomas reveal immunohistochemical expression of PLAP
, OCT3/4 and c-kit; embryonal carcinomas show positivity for CD30, PLAP
, a-fetoprotein, keratin, and human chorionic gonadotropin; yolk sac tumors are immunoreactive for a-fetoprotein, PLAP
, alkaline phosphatase, and keratins; and choriocarcinomas show expression of human chorionic gonadotropin, cytokeratin, PLAP
, and human placental lactogen.
In these 2 studies, the main finding is not only that OCT4 is a highly sensitive and specific marker of ovarian dysgerminoma, and testicular seminoma and embryonal carcinoma, respectively, but also that the OCT4 staining pattern was nuclear (in contrast to PLAP
and c-Kit, which show characteristically cell membrane staining), with uniformly strong staining intensity and staining extent of greater than 90%.