CLDN6 expression is reactivated in various solid adult tumor types, particularly in germ cell tumors (GCTs) and epithelial ovarian cancer, which led to the development of CLDN6-specific CAR-T cells and bispecific T cell-engaging antibodies that are currently being evaluated in basket clinical studies for adult patients [13,14]. This evidence concerns the gene CLDN6 and testicular germ cell tumor.