Case of a Large Pedunculated Biliary Cholesterol Polyp With Osseous Metaplasia

Cholesterol polyps are the most common benign gallbladder polyps and are usually seen in a background of cholesterolosis. Rarely, they can harbor foci of osseous metaplasia, which is an event of uncertain clinical significance that might be confused with cholelithiasis clinically or radiologically. Herein we report the case of a 78-year-old female with a 1.8-cm pedunculated polyp arising in the gallbladder body. Histologic examination showed microscopic foci of osseous metaplasia, characterized by heterotropic bone trabeculae rimmed by osteoblasts and surrounded by osteoclast giant cells. To the best of our knowledge, this case is the third case report of a cholesterol polyp with osseous metaplasia in the English literature. We also review the relative pathogenesis, clinical and pathologic findings, and previous reports.