In the p53 pathway, while TP53 and CDKN2A/B alterations overlapped in a subset of glioblastomas and IDH1/2-mutant astrocytomas, TP53 mutation predominated in IDH1/2-mutant astrocytomas, while CDKN2A/B alterations predominated in glioblastomas. The gene discussed is IDH1; the disease is glioblastoma.