IDH1 and glioblastoma: In contrast, IDH-wildtype astrocytoma is considered grade 4 glioblastoma GBM), even in cases without necrosis or vascular proliferations, as long as further genetic features, such as EGFR amplification, TERT promoter mutation or the combined gain of chromosome 7 and loss of chromosome 10 [+7/-10 are present (4).