Periampullary carcinoid of the ampulla of Vater presenting as an intraductal papillary mucinous tumour of the pancreas: a sheep in wolf's clothing.

estimated incidence at all anatomic sites of 1 in 12 000. Although 67% of these lesions are found within the gastrointestinal tract, fewer than 1% are located at or near the ampulla of Vater. These periampullary tumours have characteristics that set them apart from carcinoids at other sites, including strong immunohistochemical positivity for somatostatin and presence of psammoma bodies. Although extremely rare in the general population, periampullary carcinoids have a well-described association with neurofibromatosis type 1 (NF1), a genetic disorder with an incidence of 1 in 2500–3000. We describe the case of a woman who had a periampullary carcinoid that presented as an intraductal papillary mucinous tumour of the pancreas.