CDKN2A and glioblastoma: Primary GBM commonly exhibit amplification and/or mutations of the Epidermal Growth Factor Receptor (EGFR), mutations in the tumor suppressor genes Phosphatase and Tensin Homolog (PTEN) and TP53, complete loss of chromosome 10, deletion of Cyclin Dependent Kinase Inhibitor 2A (CDKN2), and mutations in the promoter of Telomerase Reverse Transcriptase (TERT).