[Duodenal neuroendocrine neoplasms (NEN): update on endoscopic and surgical management]

Duodenal neuroendocrine neoplasms (d-NEN) are rare neoplasms accounting for approximately 3% of all neuroendocrine neoplasms. They are classified into well-differentiated neoplasms (G1-G3), poorly differentiated neuroendocrine carcinomas (NEC) and mixed tumors; the majority of these tumors are nonfunctional. Some neoplasms are associated with genetic syndromes, such as multiple endocrine neoplasia type 1 or neurofibromatosis type 1. The diagnosis is made using endoscopic, laboratory, cross-sectional and molecular imaging techniques, such as gallium-68-DOTATATE PET/CT. Therapeutically, the tumor size in addition to histopathological findings, is the most important factor: tumors < 5 mm should be removed endoscopically and tumors 5-10 mm in size can also be resected endoscopically after risk assessment. Tumors > 10 mm should generally be treated surgically. An exception is the duodenal nonmetastatic gastrinoma, which should always be resected. The most important surgical interventions are local resections with lymphadenectomy or oncological pancreaticoduodenectomy, particularly for ampullary tumors, which have a higher risk of metastasis. In recent years, increasingly advanced combined surgical endoscopic techniques (rendezvous procedures) have been added to the therapeutic options but due to the oncological value have not yet been incorporated into the guidelines.