For example, the IDH1R132H mutation is by far the most predominant IDH1/2 mutation in CNS tumours (n = 7265/8026, 90.5%) whereas this mutation is present at much lower frequencies in bone (n = 49/361, 13.6%), leukemic (n = 519/2995, 17.3%) and other tumours (n = 14/129, 10.9%), and thus far has never been identified in biliary tract tumours (n = 212) (p < 0.001, chi-square test). This evidence concerns the gene IDH1 and central nervous system neoplasm.