SHH and medulloblastoma: According to the current WHO guidelines,medulloblastomas are now classified into the following molecularly definedgroups: Wnt signaling pathway (WNT)-activated, sonic hedgehog signaling pathway(SHH)-activated and tumor suppressor protein p53 (TP53)-mutant, SHH-activatedand TP53-wildtype, and non-WNT/non-SHH (i.e. group 3 and group 4).