Localization of alpha-fetoprotein and human chorionic gonadotropin to specific histologic types of nonseminomatous testicular cancer.

We used an indirect immunoperoxidase technique to localize alpha-fetoprotein (AFP) and human chorionic gonadotropin (HCG) to specific histologic types of testicular germ cell cancers. Among 20 nonseminomatous tumors studied, yolk sac tumor reacted for AFP in 13 of 15 cases, teratoma in 3 of 11 cases, and embryonal carcinoma in 3 of 14 cases. Syncytiotrophoblasts alone reacted for HCG in 14 of 15 cases, and syncytiotrophoblasts associated with choriocarcinoma reacted for HCG in 2 of 2 cases. There was a close correlation between the tissue demonstration of AFP and HCG and elevated serum levels of AFP and HCG, respectively. We conclude that in nonseminomatous testicular cancer yolk sac tumor is the primary site of synthesis of AFP, and syncytiotrophoblasts are the only site of synthesis of HCG.