IDH1 and central nervous system cancer: For tumor-specific candidate biomarkers like D-2-hydroxyglutarate (D-2-HG) in IDH-mutant gliomas, Kalinina et al.41 demonstrated a higher concentration of D-2-HG in cisternal than ventricular CSF for IDH-mutant gliomas, both of which were higher than that of lumbar CSF.