The oligodendroglial tumor entities present in the WHO 2016 CNS classification are the oligodendroglioma IDH-mutated 1p/19q co-deleted, oligodendroglioma NOS, anaplastic oligodendroglioma IDH-mutated 1p/19q co-deleted, anaplastic oligodendroglioma NOS and the highly debated entities oligoastrocytoma NOS and anaplastic oligoastrocytoma NOS, which, according to the new guideline, should be used only as exceptional exclusion diagnostics when genetic testing is not available [1]. This evidence concerns the gene IDH1 and oligodendroglial tumor.