Intrahepatic cholangiocarcinoma arising in multiple bile duct hamartomas: report of two cases and review of the literature.

Multiple bile duct hamartomas (BDHs)/von Meyenburg complexes, are tumor-like lesions of the liver. Malignant transformation in BDHs has been previously reported in very rare instances, and the most common tumor arising in this clinical setting is cholangiocarcinoma. Herein, we report on clinicopathological findings in two cases of cholangiocarcinoma occurring in liver with multiple BDHs. Histopathologically, multiple BDHs showed morphologic transition from clearly benign to dysplasia or carcinoma in situ, then to invasive carcinoma sequence of the biliary epithelium. The neoplastic epithelium showed positivity for cytokeratin 19, CA 19-9, and epithelial membrane antigen. Staining for Hep Par 1, alpha-fetoprotein, cytokeratin 20, and alpha1-antitrypsin was negative. All sections from the non-neoplastic liver in each specimen showed multiple BDHs. Any other clinically detectable primary tumor was not found. These two neoplasms were interpreted as a cholangiocarcinoma arising in BDHs. This suggested BDHs might be a risk factor of development of cholangiocarcinoma.