GBM are characterized by diverse genetic alterations, such as mutations in the isocitrate dehydrogenase (IDH) 1 or 2 genes, methylation of the O6-methylguanine-DNA methyltransferase (MGMT) promoter, the amplification of the gene encoding the epidermal growth factor receptor (EGFR) or the expression of the EGFR variant III (EGFRvIII). The gene discussed is MGMT; the disease is glioblastoma.