Diagnosis

Diagnosis

Rectal gastric heterotopia

Discussion

Heterotopia is defined as ectopic tissue present in a location separate from its normal anatomic and developmental environment. Gastric heterotopia (GH) is the presence of mature gastric tissue outside of its usual location within the stomach. GH is a benign entity that can be found in different locations within the gastrointestinal tract (the majority of cases are seen in the esophagus, duodenum, and Meckel diverticula). GH is infrequent beyond the ligament of Treitz, and very uncommon in the rectum or anus. GH may also be seen outside of the gastrointestinal tract in locations such as the nasopharynx and mediastinum.

The prevalence of GH in the esophagus and duodenum ranges from approximately 0.5 to 2% and is more common in males than females. GH can be asymptomatic or symptomatic leading to gastrointestinal bleeding, pain, or obstruction. Fistulous connections between the bladder and rectum, and between the anus and skin have been reported in rectal GH. GH can appear endoscopically as polyps or flat lesions and histologically as oxyntic or antral-type gastric mucosa.

The cause of gastric heterotopia is not well understood; however, theories have been proposed to explain the etiology. Ectopic gastric mucosa in the proximal gastrointestinal tract including the esophagus, gallbladder, and proximal duodenum may be due to complications during embryologic development of the stomach. However, this theory does not explain the presence of gastric tissue in the colon, rectum, and upper portion of the anal canal. GH could also arise from anomalous differentiation of gut epithelial tissue into gastric mucosa secondary to an unknown process. Finally, ectopic gastric mucosa could result from cells left behind during the descent of the stomach during the embryonic period.

The presence of gastric mucosa outside the stomach can rarely progress to dysplasia and malignancy. Adenocarcinoma of the esophagus, small bowel, and transverse colon have been reported arising from gastric heterotopia.

The interesting and challenging aspect of our case lies in the absence of any colonic mucosa in the initial biopsy. This unusual finding prompted the pathologist to consider alternative explanations, such as the possibility of a potential specimen switch. The findings of oxyntic-type gastric mucosa intermixed with rectal mucosa in the endoscopic mucosal resection specimen confirmed the biopsy findings and the diagnosis of GH.  

References

1. Iacopini F, Gotoda T, Elisei W, et al. Heterotopic gastric mucosa in the anus and rectum: first case report of endoscopic submucosal dissection and systematic review. Gastroenterol Rep 2016;196-205.

2.  Yu L, Yang Y, Cui L, Peng L, Sun G. Heterotopic gastric mucosa of the gastrointestinal tract: prevalence, histological features, and clinical characteristics. Scand J Gastroenterol. 2014;49:138-44.

3. Srinivasan R, Loewenstine H, Mayle JE. Sessile Polypoid Gastric Heterotopia of Rectum: A Report of 2 Cases and Review of the Literature. Archives of Pathology & Laboratory Medicine. 1999;123:222-224.

4. Dinarvand P, Vareedayah AA, Phillips NJ, Hachem C, Lai J. Gastric heterotopia in rectum: A literature review and its diagnostic pitfall. SAGE Open Med Case Rep. 2017;5:2050313x17693968.

5.  Murray FE, Lombard M, Dervan P, Fitzgerald RJ, Crowe J. Bleeding from multifocal heterotopic gastric mucosa in the colon controlled by an H2 antagonist. Gut. 1988;29:848-51.

6.  Ko H, Park SY, Cha EJ, Sohn JS. Colonic adenocarcinoma arising from gastric heterotopia: a case study. Korean J Pathol. 2013;47:289-92.

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