IDH1/2 mutations were found in 156 of 214 (72.9%) of tumors examined, including 59 of 86 (68.6%) diffuse astrocytomas, 17 of 18 (94.4%) oligodendrogliomas, 34 of 38 (89.5%) oligoastrocytomas, 37 of 63 (58.7%) anaplastic astrocytomas, 6 of 6 (100%) anaplastic oligodendrogliomas and 3 of 3 (100%) anaplastic oligoastrocytomas. This evidence concerns the gene IDH1 and anaplastic oligodendroglioma.