SHH and medulloblastoma: Medulloblastomas arise from the cerebellum, vermis or fourth ventricle/posterior fossa and split up in 4 different molecular subgroups: wingless (WNT)-activated (TP53wt), wingless (WNT)-activated (TP53mut), sonic hedgehog (SHH)-activated (TP53wt), MB without WNT/SHH activation (Group 3 or Group 4 (G3/4)) as defined in the 2021 WHO classification (14, 15).