Mesenchymal GBM, characterized by extensive necrosis, inflammatory markers, the upregulation of interstitial and angiogenesis genes, frequent deletions of the tumor suppressor genes tumor protein 53 (p53), PTEN and NF1 and highly expressed genes such as VEGF-A, VEGF-B, ANG1, and ANG2, represents the most aggressive subtype with limited treatment success21 (Fig. 2). The gene discussed is PTEN; the disease is glioblastoma.