IDH1 and glioblastoma: In addition to the entity-defining markers, we evaluated the frequency of three genomic alterations that are currently considered in the grading of diffuse astrocytomas: TERTp mutations, EGFR amplification (molecular criteria for grade 4 glioblastoma), and CDKN2A deletion (molecular criterion for a grade 4 IDH-mutant astrocytoma).