There are some molecular markers still under evaluation, but several are commonly tested as part of the routine clinical interrogation of GBM patients including O6-methylguanine DNA methyltransferase (MGMT), isocitrate dehydrogenase (IDH), epidermal growth factor receptor (EGFR), VEGF, tumor suppressor protein TP53, phosphatase and tensin homolog (PTEN), p16INK4a gene, phospholipid metabolites, cancer stem cells, and recently also imaging biomarkers (Table 2). The gene discussed is EGFR; the disease is cancer.