Glioblastoma, IDH-wildtype, WHO grade 4 is defined by the absence ofIDH1/IDH2mutations and the absence of histone H3 alterations in a diffusely infiltrating astrocytoma which demonstrates one or more of the following histologic or molecular features: microvascular proliferation, necrosis,EGFRamplification,TERTpromoter mutation or entire chromosome gain of 7 with loss of 10 (27,28). Here, IDH1 is linked to astrocytoma (excluding glioblastoma).