PTPN13 and adenoma: FAP1 can present hundreds to thousands of adenomas and variable extracolonic features such as congenital hypertrophy of the retinal pigment epithelium (CHRPE), osteomas, dental abnormalities (teeth agenesis, supernumerary teeth, odontomas), desmoid tumours, adrenal masses, or other associated tumours (thyroid, liver, bile ducts, pancreas, central nervous system).