ESR1 and germ cell tumor: It has been demonstrated that GPER is overexpressed in human seminomas, compared with normal testis, and in a seminoma cell line in comparison with a normal spermatogonial cell line.22 Expression of ERα and ERβ in germ cell tumors has been evaluated and compared with normal testis.40 ERβ expression was found in the majority of tumor cells, however, at lower levels when compared with expression in germ cells of the normal testis.