S100A4 and biliary atresia: In biliary atresia, in particular, the mesenchymal markers vimentin, and S100A4 (also known as fibroblast-specific protein 1), and an essential transcription factor for EMT, Snail, are expressed but the biliary-type cytokeratin CK19 and the common epithelial marker E-cadherin are not, in BECs of extrahepatic bile ducts and peribiliary glands.