TEP1 and cancer: PTEN, also known as tensin-like phosphatase 1 (TEP1) or mutated in multiple advanced cancers 1 (MMAC1) was first identified as a lost or mutated phosphatase in various cancer types such as brain, breast, kidney, and prostate in 1997.2, 3, 4PTEN is the second most mutated or deleted gene after TP53 in different cancer types.5