Oligodendrogliomas are known to be mutated for telomerase reverse transcriptase promoter (TERTp), and in this report, we evaluated 112 IDH-mutant, 1p19q codeleted oligodendrogliomas for alternative lengthening of telomeres (ALT) by fluorescence in situ hybridization (FISH), and FISH for copy-number changes of CDKN2A, MYC, PDGFRA, EGFR, chromosomes+7/10, and TERT rearrangement. This evidence concerns the gene TERT and oligodendroglioma.