Phosphatase and tensin homolog (PTEN), a phosphatidylinositol-3,4,5-trisphosphate 3 (PIP3)-phosphatase that inhibits phosphoinositide-3-kinase (PI3K) pathway, blocks AKT (also known as protein kinase B) signaling activation and hence acts as a tumor suppressor. The gene discussed is PTEN; the disease is neoplasm.