PTEN hamartoma tumor syndrome (PHTS) encompasses different syndromic disorders (Cowden syndrome, Bannayan Riley Ruvalcaba syndrome, Lhermitte Duclos syndrome, Proteus and Proteus-like syndrome, juvenile polyposis of infancy, autism spectrum disorders with macrocephaly or children with macrocephaly and developmental delay/cognitive impairment), which are all associated with germline autosomal-dominant mutations of the tumor suppressor gene PTEN. Here, PTEN is linked to Cowden syndrome 1.