SHH and medulloblastoma: The updated 2021 World Health Organization (WHO) central nervous system tumor classification combined the four histologic subtypes into a single type, “Medulloblastoma, histologically defined.” The 2021 WHO classification further elaborated the medulloblastoma molecular subtypes: the SHH subgroup was divided into four groups, and the Group 3 and 4 subtypes (non-SHH, non-WNT) into eight groups [10].