The importance of PTEN as a tumor suppressor is further supported by the fact that germline mutations of PTEN commonly occur in a group of autosomal dominant syndromes, including Cowden Syndrome, which are characterized by developmental disorders, neurological deficits, and an increased lifetime risk of cancer and are collectively referred to as PTEN hamartoma tumor syndromes (PHTS) [8, 9]. This evidence concerns the gene PTEN and Cowden disease.