This is true for Cowden (CS) and Bannayan-Riley-Ruvalcaba (BRRS) syndromes, whereby only a subset of patients have germline mutations in PTEN. Due to advances in biomedical research, we now know that there are multiple cancer-related genes besides PTEN. Importantly, these genes had not been examined in CS and BRRS patients. The gene discussed is PTEN; the disease is Cowden syndrome 1.