TERT promoter mutations are the most frequent molecular alterations seen in IDH-wildtype glioblastoma, and while some studies argue that TERT promoter mutations are sufficient for the diagnosis of glioblastoma and predict poor prognosis [75,97,98], other studies suggest they have poor specificity as they can be encountered at an equal or greater frequency in oligodendroglioma and melanoma, and may not add additional prognostic information when other histological or molecular diagnostic criteria are met for IDH-wildtype glioblastoma [96,99,100]. The gene discussed is IDH2; the disease is oligodendroglioma.