ABSTRACT
The PTEN hamartoma tumor syndrome (PHTS) includes not only the entity Cowden syndrome (CS, MIM 158350) which is the focus of this chapter, but also Bannayan-Riley-
Ruvalcaba syndrome (BRRS, MIM 153480), Proteus syndrome (PS, MIM 176920), and
Proteus-like syndrome (PSL) (1). Disorders in this heterogeneous group are all, to varying
degrees, associated with germline mutations of the PTEN tumor suppressor, localized to 10q23.2 (2,3). PTEN is a dual-specificity phosphatase, having both phospholipid and
protein phosphatase activities (4-6). PTEN plays a crucial role in controlling cell growth,
cell spreading, and mediating apoptosis and cell cycle arrest.
