It is important to note that gliomas with concurrent TERT promoter and IDH mutations are almost always accompanied with 1p19q co-deletion, which is the hallmark of oligodendroglioma according to the WHO classification 2016, and it can help to explain why gliomas with coexisting IDH and TERT promoter mutations are most likely associated with favorable outcome. This evidence concerns the gene IDH1 and oligodendroglioma.