The co-occurrence of IDH mutations with other genetic aberrations such as 1p/19q co-deletion, loss of function mutations in the alpha thalassemia X-linked intellectual disability gene (ATR-X), and inactivation of the tumor suppressor protein 53 (TP53) serve as distinct markers enabling genetic and histopathological classification of LGG tumors into oligodendrogliomas and astrocytomas (3). The gene discussed is IDH2; the disease is oligodendroglioma.