RESUMEN
Under normal circumstances, gastric mucosa only exists within the stomach. However, in certain situations, gastric mucosal tissue may undergo ectopia, commonly occurring in the esophagus and intestine, with rare occurrences within the stomach itself. A comprehensive literature review was performed to understand the distinct characteristics of ectopic gastric mucosa (EGM) in the stomach and investigate a rare incident of this disease, providing an in-depth analysis of the clinical, histopathologic, and differential diagnostic findings. The case was a 47-year-old man with acid reflux, heartburn, abdominal distension, and diarrhea (5-10 times daily) for >10 years. A gastroscope indicated a submucosal protuberance lesion in the gastric body that felt hard with biopsy forceps. A well-defined nodule under the mucosal muscle was revealed microscopically, composed of epithelial elements and no atypia. Immunohistochemical staining demonstrated similar EGM expression patterns compared with normal gastric mucosa. The present case report highlights the importance of accurate EGM diagnosis and understanding.