The significant mutations commonly found in gliomas include: IDH1/IDH2 mutations present in lower-grade gliomas and secondary GBs and associated with better prognosis; telomerase reverse transcriptase (TERT) promoter mutations common in primary GBs and associated with poor outcomes; 1p/19q co-deletion demonstrated in oligodendrogliomas and associated with better treatment responses; O-6-methylguanine-DNA methyltransferase (MGMT) promoter methylation, a biomarker for a better response to temozolomide (TMZ) chemotherapy. The gene discussed is TERT; the disease is oligodendroglioma.