IDH1 and astrocytoma (excluding glioblastoma): As initially detailed in the cIMPACT-NOW update 3 [9] along with TERT-promoter mutation, the presence of EGFR amplification, and/or the combination of chromosome 7 gain with chromosome 10 loss allows for a grade 4 designation in IDH-wildtype infiltrating astrocytoma irrespective of the presence of necrosis or microvascular proliferation [1, 3, 7, 9, 10, 22, 32, 41, 46].