Monolobar ductal plate malformation disease of the liver.

We herein report a unique monolobar hepatic disease composed of Caroli's disease, peribiliary cysts, ductal plate malformations, peribiliary gland proliferation, hepatolithiasis, and portal phlebosclerosis with thrombi. A 73-year-old man underwent abdominal imaging, which revealed multiple segmental dilations of the left intrahepatic bile ducts. Polycystic kidney diseases were absent. Intrahepatic cholangiocarcinoma was suspected, and extended left lobectomy of the liver was preformed. Grossly, the hepatic left lobe was atrophic, and partly replaced by fibrous tissue. The intrahepatic bile ducts were dilated (Caroli's disease), and showed small calcium bilirubinate hepatoliths. Microscopically, the intrahepatic bile duct showed non-obstructive segmental dilations (Caroli's disease), numerous peribiliary cysts, numerous ductal plate malformations, proliferation of intrahepatic peribiliary glands, and calcium bilirubinate hepatolithiasis. Portal veins showed phlebosclerosis with thrombi. Immunohistochemically, the various biliary epithelial cells were positive for cytokeratin (CK) 7, 8, 18, and 19, and for MUC6 and CD10. They were negative for MUC2 and MUC5AC. The ductal plate malformations were positive for fetal biliary antigen MUC1, but other biliary cell types were negative for MUC1. The present case resembles 'monolobar Caroli's disease'. We believe that the present monolobular liver disease was congenital in origin.