Heterotopic Gastric Mucosa in the Gallbladder: A Rare Case and Differential Diagnosis for a Gallbladder Polyp.

Heterotopia or ectopic tissue refers to the presence of normal tissue in an abnormal location, away from its typical anatomic site. While heterotopia is not uncommon, its occurrence in the gallbladder is quite rare, and even more unusual is the presence of gastric heterotopia within the gallbladder. This case report describes a 41-year-old female patient with oxyntic-type heterotopic gastric mucosa in the proximal body of the gallbladder. She initially visited the hospital for a routine follow-up for her degenerative joint disease when a gallbladder mass was incidentally discovered. Imaging revealed a circumferential, nodular wall thickening and enhancement of the proximal gallbladder body, along with mild diffusion restriction. Due to concern for primary gallbladder malignancy, a cholecystectomy was performed. Intraoperatively, the gallbladder appeared anatomically normal, with several adhesions and mild inflammation, prompting the omission of an intraoperative frozen section. Histopathologic analysis revealed oxyntic-type gastric mucosa within the gallbladder wall. Although this case of gastric heterotopia was benign, prolonged presence of gastric tissue in the gallbladder may lead to complications, such as ulceration, dysplasia, or even malignant transformation.