IDH1 and central nervous system cancer: We and others have previously reported a reproducible extracellular metabolome across a diverse array of gliomas, including elevated D-2-hydroxyglutarate (D-2-HG) within gliomas harboring a mutation in isocitrate dehydrogenase 1 (IDH1) [7], the most common glioma subtype in most young adult patients [8].