IDH1 and glioblastoma: According to the current WHO CNS classification of gliomas in 2021, among grade 4 diffuse gliomas in adults, we can distinguish grade 4 glioblastoma multiforme (GBM) IDH wild type, diffuse hemispheric glioma with H3 G34 mutation, and in some cases, astrocytoma with IDH mutation, previously diagnosed as a multifocal glioma with IDH mutation.