IDH2 and glioblastoma: Additional molecular distinguishing features of GBM IDH-wildtype are significantly higher frequencies of CDK4 and MDM2 amplification in high-grade F3T3 gliomas (22% vs. 7% for CDK4 amplification; 20% vs. 4% for MDM2 amplification) [16], whereas MGMT promoter methylation is similarly frequent in the two tumors [16,28].