PTEN hamartoma tumour syndrome: variability of an entity

owden syndrome (CS; OMIM 158350) is an autosomal dominant disorder with age related penetrance characterised by mucocutaneous lesions, macrocephaly and an increased risk of cancer, especially of the breast, thyroid and endometrium. 1 2 The phenotype in CS has proven to be highly variable, which became especially evident after identification of the susceptibility gene PTEN. 3 4 This is also shown in the change in incidence figures, which were found to be at least five times higher after PTEN was identified (estimated incidence before PTEN identification 1:1 000 000, 5 and after .1:200 000. 6 7 ). Bannayan-Riley-Ruvalcaba syndrome (BRRS; OMIM 153480) is allelic to CS and is characterised by the triad of macrocephaly, lipomas, and pigmented macules of the glans penis. 8 Proteus syndrome (PS; OMIM 176920) is a disorder characterised by overgrowth of hands and/or feet, asymmetry of limbs, connective tissue, and epidermal naevi, vascular and lymphatic malformations, and cranial hyperostosis. 8 Proteus-like syndrome (PLS) is another closely related disorder, where individuals are characterised by the presence of macrocephaly, lipomas and overgrowth not meeting the criteria for CS, BRRS, or PS. 8 Germline PTEN mutations have been found in 80% of individuals with CS, 60% of individuals with BRRS, up to 20% with PS, and 50% with PLS. 9 10