Mutations in the enzyme isocitrate dehydrogenase 1 (IDH1), common in a major subset of primary human brain cancers were recently shown to produce the oncometabolite 2-hydroxyglutarate with a role in the formation and the malignant progression of glioma; PTEN is also commonly lost in glioblastoma [19]–[21]; Our results suggest that they occur together less than would be expected by chance. The gene discussed is PTEN; the disease is brain cancer.