Gastric heterotopia in the rectum: a rare entity with potential pitfalls

Gastric heterotopia (GHT) is a medical condition where the gastric mucosa is found at a non-phyysiological part of the body. GHT can present itself anywhere in the gastrointestinal tract from the mouth to the anorectal area, as well as in the hepatobiliary system. However, it is relatively rare to find GHT in the rectum, with only around 50 documented cases reported in medical literature. We present the case of a 51-year-old man who underwent average-risk screening colonoscopy. He had no clinically significant comorbidities and was otherwise asymptomatic, with no family history. Notable findings included a pseudopolypoid lesion in the distal rectum, adjacent to the dentate line, measuring approximately 15 mm with regular-appearing mucosa under narrow-band-imaging. Biopsy specimens showed histological characteristics of oxyntic-type gastric mucosa without inflammation or dysplasia. GHT has the potential to progress to malignancy, although the rate of malignancy is currently unknown. Awareness of this entity is important given its frequency and potential for misdiagnosis.