IDH1 and glioblastoma: According to the 2021 WHO classification of central nervous system tumors, a diffuse IDH-wildtype astrocytoma can be classified as a glioblastoma if it meets any one of the following five criteria: microvascular proliferation, necrosis, TERT promoter mutation, EGFR gene amplification, or chromosome copy number alterations (+7/–10) (3).