A case of biliary cystadenocarcinoma with morphologic and histochemical features of hepatocytes

A case of biliary cystadenocarcinoma is presented in which the lesion seemed to partially differentiate into hepatocellular carcinoma. This patient had a cystic tumor in the left lobe of the liver, the interior being filled with papillary tumors. Histologic examination disclosed papillary growth of columnar tumor cells, together with tumor cells akin to hepatocytes (they had a distinct cell boundary, nuclear membrane, and nucleolus) showing a cobblestone appearance in some areas. Electron microscopic examination of this area showed bile canalicular structures. Histochemically, the tissue stained positively with the Luna-Ishak canalicular (LIC) technique; periodic acid-Schiff (PAS) staining demonstrated coexisting glycogen granulo-positive cells and mucus-producing cells. Thus, in this biliary cystadenocarcinoma, some tumor cells demonstrated the morphologic and histochemical features of hepatocytes.