MYC and medulloblastoma: The Group 3, representing 19% of all medulloblastomas, is composed of three different subgroups: the subgroup 3α, corresponding to 47% of MBGrou3, predominantly occurring in infants (<3 years) and frequently displaying a metastatic dissemination at diagnosis; the subgroup Group 3β, representing 21% of MBGroup3, characterized by frequent GFI activation, and less frequently metastatic than the two other subgroups 3; the subgroup Group 3γ, corresponding to 28% of MBGroup3, is characterized at molecular level by frequent MYC amplification and by a poor prognosis.