IDH1 and glioblastoma: IDH-mutant astrocytomas are now stratified into three WHO grades: astrocytoma, IDH-mutant, WHO grade 2; astrocytoma, IDH-mutant, WHO grade 3 (instead of anaplastic astrocytoma, IDH-mutant, WHO grade 3); and astrocytoma, IDH-mutant, WHO grade 4 (replacing the former term ‘glioblastoma, IDH-mutant, WHO grade 4’)3.