Background: Gastric heterotopia (GH) is the presence of gastric mucosa outside its normal anatomical location. Although commonly reported in the upper gastrointestinal tract, GH in the rectum is rare, with fewer than 100 cases documented. GH may be congenital (heteroplasia) or acquired (metaplasia) and can present with nonspecific gastrointestinal or anorectal symptoms. Furthermore, the risk of transformation of heterotopic gastric mucosa to malignancy is currently unknown, but cases of malignant transformation are described in the literature. 

Case Presentation: We report the case of a 19-year-old man presenting with chronic abdominal burning, bloating, early satiety, and constipation. Initial investigations were unremarkable. A colonoscopy revealed a well-demarcated, granular lesion with rolled borders in the distal rectum, biopsied and confirmed as gastric heterotopia. The lesion was successfully resected en-bloc via endoscopic submucosal dissection. Histopathology confirmed gastric heterotopia without dysplasia or malignancy. At six-month follow-up, there were no signs of recurrence, and patient reported partial improvement of the symptoms. 

Conclusion: Rectal gastric heterotopia is a rare entity that can mimic other anorectal conditions and has a yet unknown risk of transformation to malignancy. Diagnosis requires histopathological confirmation. Endoscopic resection via ESD is an effective and minimally invasive treatment option. Awareness of this condition can facilitate timely diagnosis and appropriate management.