PTEN hamartoma tumor syndrome (PHTS) is recognized as a spectrum of disorders caused by pathogenic variants of the tumor suppressor gene PTEN, including Cowden syndrome (CS) and Bannayan–Riley–Ruvalcaba syndrome (BRRS), which are caused by germline variants, and PTEN-related Proteus syndrome (PS) and Proteus-like syndrome, which are caused by mosaic variants [25]. This evidence concerns the gene PTEN and Cowden syndrome 1.