Multicystic biliary hamartoma: a hitherto undescribed lesion

SummaryIn this report, we presented 3 cases of unusual hamartomatous nodules of the liver. These nodules were located around hepatic capsule of the left hepatic lobe and characteristically protruded from the liver. Histologically, these nodular lesions consisted of ductal structures, periductal glands, and fibrous connective tissues containing blood vessels. Smooth muscle bundles focally surrounded ductal structures. Bile-like materials were observed within some ducts. Two cases were associated with xanthogranulomatous inflammation around bile-like materials, and this inflammatory process extended from ductal lumens to periductal connective tissues. In contrast, the remaining case, which was not associated with inflammation, showed a honeycomb appearance. Ductal epithelium and periductal glands resembled biliary epithelium and peribiliary glands, respectively, and they also expressed biliary-type cytokeratins such as cytokeratins 7 and 19. These nodules shared pathologic characteristics of ciliated hepatic foregut cysts, such as their location (around the falciform ligament) and periductal smooth muscle bundles, but did not fulfill the diagnostic criteria (no ciliated cells and multilocular lesions). These hamartomatous nodules of the liver did not fit into any of the described categories of hepatic nodular lesions. At present, we speculate that these lesions might be related to developmental abnormalities of the biliary tract or embryonal foregut.