Intrahepatic multicystic biliary hamartoma: report of a case.

Multicystic biliary hamartoma is a very rare hamartomatous nodule in the liver, which has recently been described as a new category of hepatic nodular lesion. We herein report the case of a 55-year-old man histopathologically diagnosed with this entity following surgery. A solitary multilocular lesion in the liver was pointed out by ultrasonography during a systemic examination for a positive HBs antigen. This nodule could not be definitively diagnosed by radiologic modalities, including computed tomography, magnetic resonance imaging and arteriography. The patient underwent a partial resection of the posterior segment of the liver. The nodule was a localized lesion which measured 5 x 3 cm at the widest point and displayed a honeycomb appearance. Histologically, it consisted of ductal structures, periductal glands, fibrous connective tissues containing blood vessels, and bile-like materials and xanthogranulomatous inflammation within some ducts. Liver parenchyma was not present in the nodule and the bile ducts were not dilated in the background liver. The ductal epithelium expressed biliary type cytokeratins (CK7 and 19) in immunohistochemical studies. These histopathological features were consistent with multicystic biliary hamartoma, and we discuss this rare case in detail in this report.