Cholangiocarcinoma pathogenesis: Role of the tumor microenvironment.

Cholangiocarcinoma is a tumor that originates from the neoplastic transformation of the epithelial cells of the intrahepatic or extrahepatic bile ducts. This type of cancer is difficult to diagnose, extremely aggressive, and has very poor prognosis. It is also relatively resistant to chemotherapy and radiation therapy. Its pathogenesis is poorly understood, however it is known that the tumor microenvironment is a very important factor in the regulation of tumor angiogenesis, invasion, and metastasis. The current knowledge about the mechanisms by which these events are regulated as well as the role of the tumor microenvironment in the pathogenesis and classification of cholangiocarcinoma will be discussed.