A variant of multicystic biliary hamartoma presenting as an intrahepatic cystic neoplasm

A rare case of an intrahepatic multicystic tumor is described. A 26-year-old man visited our hospital because of abdominal discomfort. Contrast-enhanced computed tomography and magnetic resonance cholangiopancreatography revealed a 10 × 7 cm multicystic tumor of the bile duct in the right side of the liver. The gross appearance of the tumor resembled an intraductal papillary neoplasm of the bile duct, and right hepatectomy with regional lymphadenectomy was performed. Histologically, these cystic lesions were composed of variably and irregularly dilated duct structures lined by columnar epithelium resembling bile duct lining. There were no atypical cells and no papillary growth of the epithelial cells. Interestingly, the dilated ducts contained inspissated bile, and the inter-cystic parenchyma contained variable but irregularly distributed and hamartomatous hepatic parenchyma with an abnormal lobular pattern. Though it had atypical features of a hamartoma in some aspects (age, smooth muscle), this case could finally be regarded as a variant of multicystic biliary hamartoma.