title: Management of gastric and duodenal neuroendocrine tumors.
abstract: Gastrointestinal neuroendocrine tumors (GI-NETs) are rare neoplasms, like all NETs. However, the incidence of GI-NETS has been increasing in recent years. Gastric NETs (G-NETs) and duodenal NETs (D-NETs) are the common types of upper GI-NETs based on tumor location. G-NETs are classified into three distinct subgroups: type I, II, and III. Type I G-NETs, which are the most common subtype (70%-80% of all G-NETs), are associated with chronic atrophic gastritis, including autoimmune gastritis and Helicobacter pylori associated atrophic gastritis. Type II G-NETs (5%-6%) are associated with multiple endocrine neoplasia type 1 and Zollinger-Ellison syndrome (MEN1-ZES). Both type I and II G-NETs are related to hypergastrinemia, are small in size, occur in multiple numbers, and are generally benign. In contrast, type III G-NETs (10%-15%) are not associated with hypergastrinemia, are large-sized single tumors, and are usually malignant. Therefore, surgical resection and chemotherapy are generally necessary for type III G-NETs, while endoscopic resection and follow-up, which are acceptable for the treatment of most type I and II G-NETs, are only acceptable for small and well differentiated type III G-NETs. D-NETs include gastrinomas (50%-60%), somatostatin-producing tumors (15%), nonfunctional serotonin-containing tumors (20%), poorly differentiated neuroendocrine carcinomas (< 3%), and gangliocytic paragangliomas (< 2%). Most D-NETs are located in the first or second part of the duodenum, with 20% occurring in the periampullary region. Therapy for D-NETs is based on tumor size, location, histological grade, stage, and tumor type. While endoscopic resection may be considered for small nonfunctional D-NETs (G1) located in the higher papilla region, surgical resection is necessary for most other D-NETs. However, there is no consensus regarding the ideal treatment of D-NETs.
authors: Yuichi Sato, Satoru Hashimoto, Ken-ichi Mizuno, Manabu Takeuchi, Shuji Terai, Department of Gastroenterology, Niigata University Graduate School of Medical and Dental Sciences, Niigata 951-8121, Japan.
authors: Yuichi
authors: Y
authors: Sato
authors: Yuichi Sato, Satoru Hashimoto, Ken-ichi Mizuno, Manabu Takeuchi, Shuji Terai, Department of Gastroenterology, Niigata University Graduate School of Medical and Dental Sciences, Niigata 951-8121, Japan.
authors: Satoru
authors: S
authors: Hashimoto
authors: Yuichi Sato, Satoru Hashimoto, Ken-ichi Mizuno, Manabu Takeuchi, Shuji Terai, Department of Gastroenterology, Niigata University Graduate School of Medical and Dental Sciences, Niigata 951-8121, Japan.
authors: Ken-Ichi
authors: K
authors: Mizuno
authors: Yuichi Sato, Satoru Hashimoto, Ken-ichi Mizuno, Manabu Takeuchi, Shuji Terai, Department of Gastroenterology, Niigata University Graduate School of Medical and Dental Sciences, Niigata 951-8121, Japan.
authors: Manabu
authors: M
authors: Takeuchi
authors: Yuichi Sato, Satoru Hashimoto, Ken-ichi Mizuno, Manabu Takeuchi, Shuji Terai, Department of Gastroenterology, Niigata University Graduate School of Medical and Dental Sciences, Niigata 951-8121, Japan.
authors: Shuji
authors: S
authors: Terai
mesh_terms: D004379:Duodenal Neoplasms / Q000175:diagnosis / Q000473:pathology / Q000628:therapy*; D016099:Endoscopy, Gastrointestinal; D006801:Humans; D018358:Neuroendocrine Tumors / Q000175:diagnosis / Q000473:pathology / Q000628:therapy*; D013274:Stomach Neoplasms / Q000175:diagnosis / Q000473:pathology / Q000628:therapy*
keywords: Classification; Duodenal neuroendocrine tumors; Endoscopic submucosal dissection; Endoscopic treatment; Gastric neuroendocrine tumors