Solitary bile duct hamartoma of the liver.

Bile duct hamartomas, also known as von Meyenburg complexes, are benign liver malformations which usually present as multiple small nodules scattered in both lobes of the liver. We report a unique case of bile duct hamartoma. An asymptomatic 30-year-old man who had a solitary cystic lesion underwent partial hepatectomy. Macroscopically, the lesion, measuring 3.6 cm in diameter, was composed of a number of small grayish-white cysts measuring 0.1 to 1.2 cm in diameter. Histologically, the constituent cysts were embedded in a fibrous stroma and were lined by low columnar or cuboidal epithelium. By immunohistochemistry, the MIB-1 index was below 1%, and p53 and carcinoembryonic antigen (CEA) were negative. These findings lead us to conjecture that the lesion was a bile duct hamartoma, although its solitary nature and large size differed from those of typical bile duct hamartoma.