According to the most recent classification (fifth edition) of CNS tumors, developed by the World Health Organization (WHO), GBM represents the most lethal form of isocitrate dehydrogenase (IDH)-wild type diffuse adult-type astrocytoma, where the methylation status of the promoter of O6-methylguanine-DNA methyltransferase (MGMT) gene is a prognostic factor [2]. This evidence concerns the gene MGMT and astrocytoma (excluding glioblastoma).