The studies related in this area showed that ESC could participate in spermatogenesis by forming functional male germ cells in vitro or by supporting the maturation of primordial germ cells into haploid male gametes [ 19– 219.
In these cases of multiple germ cell tumours, strong theoretical and clinical data suggest an underlying common pathogenetic mechanism concerning genetic instability or abnormalities during the pluripotent embryonic differentiation and maturation of the germ cell.
Testicular tissue includes Leydig cells, which produce androgenic hormones, and Sertoli cells, which form the structure of the seminiferous tubules and support the production and maturation of the germ cells that develop into sperm.
Another method based on three-dimensional testicular cell culture in soft agar has been recently described to allow the progression of prepuberal spermatogonia into meiosis and further maturation of the germ cells into morphologically normal spermatozoa, although with very low efficiency.
Rodent studies have provided some insight into the maturation of the germ cell lineage in fetal/neonatal life (Wilhelm et al., 2007), but their usefulness is limited as neither CIS nor TGCT occur spontaneously, nor can be induced, in the rodent testis.
