An Unusual Duodenal Finding

Question: A 72-year-old woman with a medical history of gastroesophageal reflux disease, obesity, acquired hypothyroidism, diabetes mellitus, hypertension, and diverticulosis presented with proton pump inhibitor–refractory dyspepsia. Esophagogastroduodenoscopy demonstrated a normal esophagus and stomach, but an unusual 20 × 18 mm glandular Paris IIa lesion was found in the duodenal bulb with a normal second portion of the duodenum. Endoscopic and histologic findings are shown in Figures A and B. What was the most likely diagnosis? Look on page 195 for the answer and see the Gastroenterology website (www.gastrojournal.org) for more information on submitting to Gastro Curbside Consult. Gastric heterotopia (GH) is a rare congenital condition where gastric tissue is found at a location outside the stomach. It may be found anywhere in the GI tract from mouth to anus and is found in the duodenal bulb in 0.5%-2% of individuals, where it most commonly appears as single or multiple asymptomatic polypoid lesions.1Khan S. Niaz S. Khan M. et al.A case of heterotopic gastric tissue in duodenal bulb: an interesting endoscopic finding.Cureus. 2022; 14e24271Google Scholar Large lesions may ulcerate (secondary to acid secretion), bleed, intussuscept, or obstruct, but that is uncommon. Histologically, GH shows aggregates of oxyntic glands composed of chief and parietal cells, and the overlying surface often exhibits gastric foveolar mucinous epithelium (apical mucin cap),2Maione F. Chini A. Gennarelli N. et al.Endoscopic resection of a large polypoid gastric heterotopia of duodenum: a case report.Clin Case Rep. 2021; 9e04633Crossref Google Scholar as demonstrated in the left portion of Figure B. The right portion of Figure B demonstrates normal duodenal mucosa (villi lined by goblet cells, absorptive epithelium, and rare Brunner’s glands). It is important to distinguish GH from the more common acquired condition gastric metaplasia (GM). GM involves the villous surface epithelium of the duodenum, and the metaplastic cells contain small apical vacuoles, similar to gastric foveolar cells, also known as gastric foveolar metaplasia. GM is a reactive process, often associated with duodenal mucosal injury/inflammation, which may or may not be due to Helicobacter pylori (HP) infection. In contrast, GH is not associated with HP, it shows normal duodenal mucosa in the background, and has an association with fundic gland polyps, possibly due to an indirect association through PPI therapy enhancing the endoscopic prominence of GH.3Narang Natasha et al.Gastric tissue in the duodenal bulb: heterotopia or metaplasia?.Am J Gastroenterol. 2020; 115: S1446Crossref Google Scholar Importantly, oxyntic glands characteristic of GH are not identified in GM. Finally, GH often manifests as nodular mucosa endoscopically, whereas GM is detected microscopically. It has been suggested that GH may have neoplastic potential.3Narang Natasha et al.Gastric tissue in the duodenal bulb: heterotopia or metaplasia?.Am J Gastroenterol. 2020; 115: S1446Crossref Google Scholar Therefore, accurate endoscopic and pathologic identification may be important, although it will require further investigation to determine if endoscopic surveillance is warranted.