Well-Differentiated Grade 1 Gastric Neuroendocrine Tumor Occurring 11 Years After Pernicious Anemia

Type I gastric neuroendocrine tumors (GNETs) are closely associated with autoimmune atrophic gastritis, particularly pernicious anemia. They arise as a consequence of chronic hypergastrinemia, which induces enterochromaffin-like cell hyperplasia and subsequent neoplastic transformation. We report the case of a 34-year-old woman followed since 2014 for pernicious anemia, in whom a well-differentiated grade 1 gastric neuroendocrine tumor was diagnosed in 2025—11 years after the initial diagnosis. Endoscopy revealed multiple polypoid lesions in the gastric fundus. Histology and immunohistochemistry confirmed a well-differentiated NET (Ki-67 index: 1%; chromogranin A and synaptophysin positive) arising in the setting of autoimmune fundic gastritis with severe glandular atrophy and both pseudopyloric and intestinal metaplasia. Staging evaluations showed no metastatic spread. The patient underwent total gastrectomy, and final pathology revealed a NET staged pT1bN1M0. Following surgery, biological markers normalized (gastrin: 32 pg/mL; chromogranin A: 25 ng/mL). This case highlights the well-established pathophysiological link between pernicious anemia and type I gastric NETs and underscores the importance of long-term endoscopic surveillance in patients with autoimmune atrophic gastritis.