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Objectives: The pathogenesis for non-type 1/2 gastric neuroendocrine tumors (G-NETs) remains unclear. The aim of this study was to examine the clinicopathologic features of G-NETs and associated mucosal changes., Methods: The electronic health records of patients with non-type 1/2 G-NETs were reviewed. H&E slides were reviewed for pathologic features and mucosal changes. The t test and Fisher exact test were used for statistical analysis., Results: In total, 33 patients were assigned to either group 1 (n = 23) or group 2 (n = 10). Group 1 included patients with a history of proton pump inhibitor (PPI) use, increased gastrin levels, or significant PPI effect (PPI/gastrin-associated). All other patients were assigned to group 2. There was no significant difference in age and sex between the 2 groups. Group 2 tumors were more likely to be larger, invade deeper, and develop metastases (P < .05). Tumors in patients with cirrhosis tended to be larger. Peritumoral mucosal changes included loss of oxyntic glands, foveolar hyperplasia, and intestinal metaplasia. Background mucosa in group 1 patients showed PPI effect and neuroendocrine hyperplasia or dysplasia., Conclusions: Although PPI/gastrin-associated non-type 1/2 G-NETs were smaller and more indolent than typical type 3 G-NETs, tumors in patients with cirrhosis tended to be larger. Additionally, peritumoral mucosal changes could mimic chronic atrophic gastritis., (© The Author(s) 2023. Published by Oxford University Press on behalf of American Society for Clinical Pathology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)