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World J Gastroenterol. Aug 14, 2016; 22(30): 6817-6828
Published online Aug 14, 2016. doi: 10.3748/wjg.v22.i30.6817
Management of gastric and duodenal neuroendocrine tumors
Yuichi Sato, Satoru Hashimoto, Ken-ichi Mizuno, Manabu Takeuchi, Shuji Terai
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
Yuichi Sato, Division of Endoscopy, Niigata University Medical and Dental Hospital, Niigata 951-8121, Japan
Author contributions: Sato Y designed and wrote the manuscript; Hashimoto S, Mizuno K, Takeuchi M and Shuji T had critical discussions regarding the manuscript with Sato Y.
Conflict-of-interest statement: The authors declare that no financial or other conflicts of interest exist in relation to the content of this article.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Yuichi Sato, MD, Department of Gastroenterology, Niigata University Graduate School of Medical and Dental Sciences, Asahimachi-dori, Niigata 951-8121, Japan. yuichi@med.niigata-u.ac.jp
Telephone: +81-25-2272207 Fax: +81-25-2270776
Received: March 14, 2016
Peer-review started: March 16, 2016
First decision: March 31, 2016
Revised: June 16, 2016
Accepted: July 6, 2016
Article in press: July 6, 2016
Published online: August 14, 2016
Processing time: 142 Days and 18.7 Hours
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.

Keywords: Gastric neuroendocrine tumors, Duodenal neuroendocrine tumors, Classification, Endoscopic treatment, Endoscopic submucosal dissection

Core tip: There is a significant increase in the incidence of gastric and duodenal neuroendocrine tumors (G-NETs and D-NETs). G-NETs are classified into three distinct subtypes based on tumor etiology. There are important differences between each type in terms of clinical presentation, prognosis, and management strategies. D-NETs include five histological types. The majority of D-NETs are located in the first or second part of the duodenum. The choice of treatment for D-NETs is based on tumor size, location, histological grade, stage, and tumor type.