IDH2 and central nervous system cancer: Sixty-six of the 69 gliomas were IDH-mutant: 61 had IDH1 R132H mutations detected by immunohistochemistry (IHC); 5 had IDH2 mutations detected at sequencing analysis, including 2 ODs and 1 AOD with a R172K mutation and 2 AODs with a R172M mutation.