Abstract
Duodenal neuroendocrine tumours (NETs) including “carcinoids” comprise 16.5% of all gastrointestinal NETs in Japan and are increasing in prevalence in Western countries where they currently account for only 2 - 3% of gastrointestinal NETs. The 2010 WHO classification defined a carcinoid as NET G1, which is well differentiated and has low proliferative activity. However, small duodenal NETs are usually asymptomatic except for the ampullary carcinoid causing obstructive jaundice. Most tumors express hormonal production immunohistochemically, but clinically are almost hormonally silent and rarely develop into the Zollinger-Ellison syndrome (ZES) presenting as a gastroduodenal ulcer and chronic diarrhoea. The carcinoid grows slowly, and metastasis to regional lymph nodes occurs even with small tumors at a rate that cannot be ignored. A definite strategy for duodenal carcinoids has not yet been established. Tumors which invade the muscular layer or metastasis to the paraduodenal lymph nodes need radical resection such as a pancreaticoduodenectomy. For small, non-metastatic carcinoids of the 1st portion limited to the submucosa, endoscopic resection is one optimal noninvasive procedure, while endoscopic papillectomy for the ampullary carcinoid needs further decision making. The size, location, cell type (G1∼3), functional activity and the stage of the tumour, in addition to the individual state, should be taken into consideration to obtain effective management.
