CDKN2A and glioblastoma: GBM, and lower grade glioma (LGG) datasets have shown that MTAP and CDKN2A are co-deleted in more than 40% of the cases in GBM; however, the co-deletion occurs in approximately 8% of the cases in LGG, which include astrocytoma, oligoastrocytoma and oligodendroglioma.