IDH1 and central nervous system cancer: The new WHO (World Health Organization) classification distinguishes between IDH1/2 (isocytrate dehydrogenase 1/2) mutant gliomas, which include lower-grade gliomas (LGGs) (grade 2–3) and grade 4 IDH1/2 mut gliomas, and IDH1/2 wild-type glioblastomas (GBMs).