Hepatic nodular hamartoma containing liver cysts, ductal plate malformations and peribiliary glands

An 83‐year‐old man with hepatocellular carcinoma was found to have a low‐echoic and low‐density tumor measuring 7.2 cm × 5.6 cm. Caroli's disease was absent. Clinical diagnosis was intrahepatic cholangiocarcinoma. Three cores of liver biopsy were obtained from the tumor. Histologically, it consisted of liver cysts, ductal plate malformations, peribiliary glands, hepatocytes, portal tracts and mesenchymal tissue. Apparent features of cirrhosis were not found. The liver cysts were lined by a layer of cuboidal cells with multiple papillary protrusions. The ductal plate malformations resembled fetal ductal plates. The peribiliary glands were seromucous glands. Immunohistochemically, these abnormal ductal structures showed positive reaction to biliary type cytokeratins, namely, cytokeratin (CK)7, CK8, CK18 and CK19. Mucin gene expression showed that these biliary structures are positive for fetal antigen MUC1. MUC6 is also positive in them. Aberrant expression of CD10 was observed in these biliary structures. MUC2, MUC5AC and CDX2 were negative. The author thinks that this lesion is hepatic hamartoma with ductal plate malformations, liver cysts and peribiliary glands. To the best of the author's knowledge, this type of liver nodule has not been reported in the published work.