In our study, IDH1 (R132H) expression was detected in 23 (92%) oligodendrogliomas cases, 12 (80%) anaplastic oligodendrogliomas cases, 1 (100%) oligodendrogliomas NOS case, 12 (85.7%) A cases, 3 (75%) anaplastic astrocytoma cases, and 1 (100%) anaplastic oligoastrocytomas case. This evidence concerns the gene IDH1 and anaplastic oligodendroglioma.