TERT and oligodendroglioma: TERT mutations are usually investigated by sequencing or real-time PCR (7), and TERT promoter mutations occur in 70-80% of glioblastomas (GBM), 95% of oligodendrogliomas (OD), and 10-25% of astrocytomas (5). TERT promoter mutations are significantly inversely proportional to IDH1 / 2 mutations (8).