IDH2 and central nervous system cancer: In contrast, the large majority of grade IV astrocytomas are TERT-mutated only (74%), while double- and triple-positive gliomas are very rare (<1% and 2%, respectively), 7% were IDH only-mutated, and 17% triple-negative [156]; the prognosis is negative for all grade IV astrocytomas and particularly for those TERT-only mutated [156].