According to the current WHO classification of CNS tumors (2021), MB comprises four major molecular groups: MB, WNT-activated (WNT-MB); MB, SHH-activated (SHH-MB) TP53-wildtype; MB, SHH-activated TP53-mutant; and MB, non-WNT/non-SHH. The gene discussed is SHH; the disease is central nervous system neoplasm.