Neuroendocrine Neoplasms of the Stomach

Abstract

Based on rising incidence in recent decades, gastric neuroendocrine tumors (G-NETs) or gastric carcinoids (GCs) are being increasingly identified at endoscopy, both as polypoid and nonpolypoid gastric lesions. There are four types of G-NETs with important epidemiological, pathophysiological, histopathologic, and endoscopic differences that affect their diagnosis, prognosis, and patient management. The underlying pathogenetic mechanism, hypergastrinemia, results from achlorhydria in patients with chronic atrophic gastritis (type I G-NETs) and from gastrinoma in patients with MEN1 (multiple endocrine neoplasia type I) syndrome (type II G-NETs). Both ECL-cell dysplasia and severe hyperplasia increase risk for G-NET development in type A chronic atrophic gastritis with hypergastrinemia/G-cell hyperplasia. Type III G-NETs occur sporadically, independent of gastrin levels. The histologic typing, grading, and Ki67 index are important for prognostication and patient management. Type I G-NETs 1 cm should be resected due to small risk of lymph node metastases. Both type I G-NETs >1 cm and type II G-NETs should be evaluated for invasion beyond the submucosa prior to endoscopic resection. Type III G-NETs should be managed similar to gastric adenocarcinoma. The treatment of advanced G-NETs needs to be multimodal and best accomplished in subspecialty referral centers with advanced clinical, pathologic, and imaging expertise. In order to succeed with more personalized patient management strategies, analytical and clinical validation of relevant biomarkers will be critical in the near future.