Background:PLAP exist in the placenta and can express in ovarian germ cell tumor, testis and extragonadal germ cell tumors, including seminoma, embryonal carcinoma, gonadoblastoma, yolk sac, and choriocarcinoma, etc. But PLAP do not express in seminomatous seminoma and immature teratoma. PLAP is mainly used for differential diagnosis and auxiliary diagnosis of placental trophoblastic tumor, ovarian germ cell tumor, testis and extragonadal germ cell tumors.