Clinical Aspects of Gastric and Duodenal Neuroendocrine Neoplasms

With the development of endoscopy, the incidence of gastric andduodenal neuroendocrine neoplasms (NENs) has increased in recentdecades. In the 2010 World Health Organization (WHO) classification,well-differentiated NENs were classified into NET G1 or G2,which is equivalent to the carcinoid tumor. Poorly differentiatedNENs were named neuroendocrine carcinoma (NEC). Gastric NENsare classified into four types in accordance with their characteristics.Type 1 generally appears as multiple polypoid tumors at the fundusand corpus and takes a benign course. Type 2 has morphologicallysimilar characteristics to type 1 and is associated with Zollinger-Ellisonsyndrome. Endoscopic treatment should be considered for casesin which the tumor is less than 2 cm and confined to mucosa and submucosa.In type 1 and type 2 accompanying hypergastrinemia, if thetumor was less than or equal to 1 cm, observation without endoscopicresection may be considered. Type 3 occurs sporadically and requiresaggressive surgical treatment, including gastric resection and lymphnode dissection due to poor prognosis. Poorly differentiated neuroendocrinecarcinomas were classified as type 4. Although type 4 tumorsare usually inoperable, surgery is sometimes performed with the aimof reducing tumor volume. Somatostatin analog, interferon alpha,and cytotoxic chemotherapy can be used with metastatic NENs. DuodenalNENs are rare compared to stomach NENs. The prognosis ofduodenal NENs depends on their size. Endoscopic resection can beperformed in small duodenal NENs. Surgery, including Whipple’sprocedure, should be considered in large tumors.