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A case of osseous metaplasia in a gastric hyperplastic polyp: An unexpected finding in a common polyp


 
 
 Foveolar hyperplastic polyp is a common gastric polyp characterized by foveolar hyperplasia with erosion, acute and chronic inflammation, granulation tissue formation, and smooth muscle strands extending from the muscularis mucosae. Although foveolar hyperplastic polyps may rarely contain foci of dysplasia or invasive carcinoma, osseous metaplasia/heterotopic bone formation in foveolar hyperplastic polyps of the stomach is extremely rare with a few case reports.
 
 
 
 A 63-year-old female with a history of hypertension, sick sinus syndrome, and Hashimoto’s thyroiditis was referred to our facility for evaluation of a mass in segment eight of the liver. The liver biopsy showed a moderately differentiated adenocarcinoma, most consistent with intrahepatic cholangiocarcinoma. A screening gastrointestinal endoscopy revealed a 7-mm sessile polyp in the antrum. The polyp was removed with a cold snare. No other abnormalities were identified in the stomach. Sections of the polyp showed fragments of antral-type gastric mucosa with foveolar hyperplasia, erosion, acute and chronic inflammation, and focal granulation tissue formation. In addition, multiple foci of woven bone formation without bone marrow surrounding dilated gastric foveolae were identified. No Helicobacter infection, intestinal metaplasia, dysplasia or malignancy was identified histologically. Osseous metaplasia/heterotopic bone formation is a well-known finding reported in various neoplastic and non- neoplastic conditions. However, osseous metaplasia in foveolar hyperplastic polyps of the stomach is extremely rare. There have been only four previous case reports published in English language. Our current case shows clinicopathologic features similar to those of the previous case reports including the findings of small-sized polyp found incidentally in middle-aged patients with no clinical history of hypercalcemia or any other abnormalities causing heterotopic bone formation.
 
 
 
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 Although the pathogenesis of osseous metaplasia in a gastric hyperplastic polyp remains unknown, the finding of osseous metaplasia in a gastric hyperplastic polyp is very intriguing.
