Direct bisulfite sequencing revealed significantly increased methylation scores of the analyzed CpG island of DIRAS-1 in IDH-mutant astrocytic as well as in IDH-mutant and 1p/19q-codeleted oligodendroglial tumors but did not detect significantly increased DIRAS-1 promoter methylation in IDH-wild-type astrocytic tumors. The gene discussed is IDH1; the disease is oligodendroglial tumor.