PTEN and cancer: Phosphatase and tensin homolog (PTEN) is a tumor suppressor gene involved in the regulation of the phosphoinositol-3-kinase and AKT signaling pathways and control of cellular proliferation and survival. PTEN is the second most frequently mutated gene in human cancers (after TP53) and germline mutations in PTEN are frequently observed in cancer susceptibility syndromes [47].