Background: The entity cholangiocarcinoma comprises various malignant epithelial neoplasms of different morphology, etiology, and pathogenesis.
Aim: In this review, the etiology, pathogenesis, diagnostic criteria, classification, and molecular alterations of intra- and extrahepatic cholangiocarcinomas are summarized.
Material and methods: This review is based on the currently available literature and personal knowledge.
Results and discussion: Cholangiocarcinomas are morphologically and molecularly diverse neoplasms that can develop ubiquitously in the biliary tract. Since there is a significant histological and immunohistochemical overlap with frequent liver metastases, a definite diagnosis can often only be rendered in the clinical context. Cholangiocarcinomas are subclassified into intrahepatic (iCCA), perihilar (pCCA), and distal (dCCA) tumors according to macro-anatomical criteria. Recent studies show that there are distinctive molecular differences in particular between iCCA and extrahepatic CCA (eCCA, including pCCA and dCCA). In addition, morphologically well-characterized precursor lesions have been identified, which in various frequencies can be assigned not only to the anatomical classification, but also to certain etiologies. An exact classification is therefore essential, especially with regard to the development of innovative, targeted therapeutic approaches.
Keywords: Biliary tract; Etiology; Molecular carcinogenesis; Pathogenesis; Precursor lesions.