SHH and central nervous system neoplasm: In the major 2016 WHO re-classification of CNS tumors, MBs were subdivided into following major molecular subgroups (8): wingless-type (WNT)-activated MBs (10%; children and adults, associated with very good prognosis); sonic hedgehog (SHH)-activated MBs (30%; intermediate prognosis, infants and adults; further characterized as TP53 mutant or TP53 wild-type); and two provisional non-WNT/SHH subgroups: group 3 MBs (25%; poor prognosis, infants and children) and group 4 MBs (35%; intermediate prognosis, children and adults) (reviewed in (17,18)).