TP53 and medulloblastoma: The most recent WHO classification of central nervous system tumors (WHO CNS 2021 5th edition) has divided medulloblastomas into four molecular subgroups: WNT-activated, SHH-activated and TP53 wildtype, SHH-activated and TP53 mutant, and non-WNT/non-SHH (previously groups 3 and 4).