There is growing evidence suggesting the importance of CDKN2A deletion as a prognostic marker for adverse clinical outcomes in several CNS tumors, including supratentorial ependymoma with ZFTA fusion [40], high-grade meningioma [41], anaplastic IDH-mutant astrocytoma, and oligodendroglioma [22]. This evidence concerns the gene IDH1 and oligodendroglioma.