Studies in human testis and vitamin D receptor (Vdr) knockout mice have shown that several bone factors such as Runt-related transcription factor 2 (RUNX2), Osterix, and osteocalcin are expressed both in normal testis as well as in testicular germ cell tumours (TGCTs)14,15. This evidence concerns the gene RUNX2 and childhood testicular germ cell tumor.