Perplexing Gastrointestinal Pathology: A Case Report on Ectopic Gastric Tissue Presenting as Rectal Mass

Abstract

Abstract Objectives Gastric heterotopia (GHT) is a commonly reported epithelial heterotopia and has been described as heteroplasia (congenital) during organogenesis or metaplasia (acquired) during process of damaged epithelial repair. GHT can occur along the GI tract from nose to anus; it is predominantly seen in esophagus, duodenum, and Meckel’s diverticulum. It is the most common subtype of epithelial heterotopia. However, the presence of gastric mucosa in the rectum is a very uncommon entity. The endoscopic prevalence of GHT can reach up to 11% in foregut and midgut with a lesser prevalence in hindgut. Methods We present an interesting case of heterotopic gastric mucosa presenting as a rectal mass. A 27-year-old female patient presented with lower abdominal pain and episodic bloody diarrhea. After initial workup, a colonoscopy was done, which showed a 3-cm mass in the rectum. Features of inflammatory bowel disease were not identified. Results At the first rectal biopsy, multiple fragments of gastric mucosa, with some minimally attached rectal crypts, were identified and a diagnosis of gastric heterotopia was made. Subsequently, the mass was resected and similar findings were identified, confirming the diagnosis. Our case showed mixed oxyntic and antral mucosa comingling with rectal-type mucosa. Immunohistochemical studies were performed, which showed CDX2 and CK20 being positive in rectal and CK7 in gastric mucosa. Conclusion Gastric heterotopia is a rare entity that can present as a solitary lesion. The clinical signs and symptoms can mimic those of inflammatory bowel disease. Floater or contamination is an important pitfall in this entity and can lead to an erroneously diagnose. Due to high frequency of having floater in some histology laboratories, we recommend ordering multiple deeper recuts on cases when the pathologist sees closeness or attachment of gastric tissue to the rectal tissue.