TP53 and medulloblastoma: Presently, MBs are classified into the following four molecular subgroups with peculiar cytogenetic, mutational, and gene expression characteristics [12]: (i) medulloblastoma WNT-activated (characterized by enhanced WNT-beta catenin pathway activation); (ii) medulloblastoma SHH-activated and TP53-mutant (characterized by activation of the SHH pathway and mutation in TP53 gene); (iii) medulloblastoma SHH-activated and TP53-wildtype (characterized by activation of the SHH pathway and absence of mutations in TP53 gene); and (iv) medulloblastoma non-WNT/non-SHH (Group 3, Group 4).