IDH2 and glioma: We discovered that CSF concentrations of pyruvate + oxaloacetic acid were significantly lower in the gliomas with IDH mutations compared with those with a wild-type IDH. In contrast, the CSF concentrations of lactic, citric, and isocitric acid were significantly higher in gliomas with IDH mutations compared with those of a wild-type IDH. In addition, the levels of the late TCA cycle metabolites that act downstream of isocitric acid decreased in the gliomas with IDH mutations.