CDK4 and central nervous system cancer: In “secondary glioma pathway”, gains of PDGFA (1 in LGG and 2 in HGG), PDGFRA (2 in LGG and 2 in HGG) and CDK4 (1 in LGG and 2 in HGG) and RB1 (2 in HGG), and losses of RB1 (1 in LGG and 2 in HGG) are also identified.