GPC3 and yolk sac tumor: This expression is consistent with the expression of GPC3 in cells with extra-embryonic differentiation including strong expression in normal placenta as well as tumors which recapitulate the phenotype of extra-embryonic membranes (amnion, yolk sac, chorion, and allantois), such as gonadal and extra-gonadal choriocarcinoma and yolk sac tumor [18].