Results: Primary glioblastomas had the highest frequency of TERT promoter mutations (25 of 28, 89.2%, p=0.006) followed by oligodendrogliomas (29 of 35, 82.8%, p<0.001) while astrocytomas showed the lowest frequency (3 of 15, 20%, p=0.107), and the positivity significantly differed among these three groups (p<0.001). TERT promoter mutations were more frequent in patients older than 55 years of age at diagnosis (p=0.023). The gene discussed is TERT; the disease is oligodendroglioma.