Immunohistochemical characterization of multicentric hepatocholangiocellular adenoma in a pig

Three spherical opaque-white tumor nodules were found in close proximity to each other in the liver of a breeding sow, postslaughter, at a veterinary food inspection. The tumor nodules were circumscribed and histologically consisted of discrete hepatocellular and cholangiocellular nests, in association with polygonal-to-oval-shaped cells with slight cellular atypia. Immunohistochemically, all cellular components were negative for carcinoembryonic antigen, but positive for p53. Both cholangiocytes and oval-shaped cells were immunoreactive to anti-cytokeratin antibodies AE1/AE3 and MNF116. In addition, cholangiocytes were exclusively immunoreactive to anti-cytokeratin antibody CAM5.2, and hepatocytes were positive for MNF116 and hepatocyte paraffin 1. All neoplastic cells were positive for the hepatic progenitor cell markers, α-1-fetoprotein, sal-like protein 4, and epithelial cell adhesion molecule. From these results, the present case was diagnosed as hepatocholangiocellular adenoma, arising from epithelial cells of the canals of Hering.