Intrahepatic Cholangiocarcinoma With Sarcomatous Transformation: Demonstrating the Transition Zone.

Intrahepatic cholangiocarcinoma with sarcomatous transformation (ICC-S) is a rare, aggressive neoplasm with epithelial and sarcomatous elements. We report a rapid progression of ICC-S in a 66-year-old woman. Initially, a seemingly benign 8-cm mass was observed. However, the tumor doubled to 16 cm within 3 months during follow-up. Partial hepatectomy confirmed ICC-S and histopathological examination showed cytokeratin 7 and vimentin positivity in epithelial and sarcomatous components, respectively. An analysis of transition zone indicated epithelial-mesenchymal transition as a mechanism for sarcomatous transformation. We provide the first detailed immunohistochemical analysis of the transition zone in ICC-S, highlighting epithelial-mesenchymal transition's role in pathogenesis.