SHH and medulloblastoma: The WHO classification of 2016, as well as the upcoming 2021 classification [28], describes five molecularly defined medulloblastoma subgroups—WNT-activated, SHH-activated/TP53 mutated, SHH-activated/TP53 wild-type, group 3, and group 4—and four histological patterns—classic, desmoplastic/nodular, with extensive nodularity, and large cell/anaplastic.