PTEN and glioblastoma: Although these pediatric tumors are histologically indistinguishable from adult glioblastomas, they exhibit some differences at the molecular level compared to the adult ones: EGFR amplification and PTEN deletion are rare in pediatric glioblastomas, despite the low frequency of PTEN abnormalities, AKT is very frequently activated in pediatric glioblastomas; TP53 mutations are frequent in pediatric glioblastomas.