In the 5 years since the discovery of PTEN, encoding a dual specificity phosphatase tumor suppressor on 10q23, it has been shown to be a susceptibility gene for an inherited cancer syndrome, Cowden syndrome, and for several developmental disorders; it has been shown to play a prominent role in normal murine and human development; and it has been shown to be instrumental in cell cycle arrest, apoptosis, and/or possibly cell migration and cytoskeletal affairs.