AbstractGastric neuroendocrine tumors (NETs) are rare and can occur in patients with chronic atrophic gastritis (type I), multiple endocrine neoplasia 1 syndrome, or Zollinger–Ellison syndrome (type II), or sporadically (type III). Types I and II gastric NETs usually present as multiple small sessile lesions and are usually found coincidentally. Type III lesions are usually larger, isolated, and responsible for iron deficiency anemia and abdominal pain. This article is part of an expert encyclopedia.