Oligodendroglioma is characterized by the co-deletion of chromosome arms 1p and 19q (1p/19q codel) along with IDH mutations (Table 1), while astrocytoma is 1p/19q non-codel with loss of alpha-thalassemia/mental retardation syndrome X-linked (ATRX). This evidence concerns the gene IDH2 and astrocytoma (excluding glioblastoma).