IDH1 and astrocytoma (excluding glioblastoma): In comparison to glioblastoma and IDH1/2-mutant astrocytoma, oligodendroglioma displayed no specific molecular alterations associated with prognosis.5 This observation suggests that higher-grade oligodendrogliomas may be characterized by a more diverse array of genomic alterations correlating with tumor grade, rather than a few dominant recurrent driver mutations dictating higher-grade behavior.