CDKN2A and glioblastoma: Only one of the de novo RRD glioblastomas had CDKN2A/B homozygous deletion (1/9, 11%), with another tumor harboring a truncating frameshift mutation in CDKN2A that was a rare mechanism of CDKN2A gene inactivation in the conventional glioblastomas (11/450, 2%).