SHH and Mobius syndrome: The 2021 fifth edition of the WHO Classification of CNS Tumors categorizes MBs into four distinct molecular subgroups: WNT-activated, SHH-activated with TP53 wild type, SHH-activated with TP53 mutation, and non-WNT/non-SHH (formerly classified as groups 3 and 4 (50, 58–60).