Cholangiocarcinoma is a malignant tumor arising from the epithelium of the bile ducts. Most of these tumors are adenocarcinomas [1]. Intra-hepatic Cholangiocarcinoma accounts for 10% of all cholangiocarcinomas, hilar Cholangiocarcinoma for 25%, and extrahepatic Cholangiocarcinoma for 65% [2, 3]. Usually, intrahepatic Cholangiocarcinoma presents as a large mass because the tumor does not cause clinical symptoms in its early stages, whereas extrahepatic Cholangiocarcinoma is usually small at the time of presentation because the bile ducts are occluded in its early stage and patients present with jaundice.
Various terminology and classifications have been used to describe the pathologic and radiologic appearance of Cholangiocarcinoma, and each describes a specific aspect of the tumor. However, some of the terminology and classifications are ambiguous and therefore confusing. Eggel [4] classified cholangiocarcinomas as nodular, massive, and diffuse, like hepatocellular carcinoma. Rosai [5] classified Cholangiocarcinoma as polypoid and sclerosing. Weinbren and Mutum [6] classified Cholangiocarcinoma into three types: nodular, sclerosing, and papillary. In the radiologic literature, hilar and extrahepatic cholangiocarcinomas have been classified as exophytic, infiltrating, and polypoid (or papillary) [7-9].
The Liver Cancer Study Group of Japan has proposed a new classification based on growth characteristics, with tumors being identified as mass-forming, periductal-infiltrating, and in-traductal-growing types [10] (Fig. 1). This classification is considered to be the most reasonable because it describes the gross appearance, growing characteristics, biologic behavior, and prognostic implication for patients [11, 12] and because it is helpful for radiologic interpretation. According to this new classification, which I use for this review article, the exophytic or nodular type matches the mass-forming type, the infiltrating or sclerosing type matches the periductal-infiltrating, and the polypoid or papillary type matches the intraductal-growing type. The prognosis for mass-forming and periductal-infiltrating cholangiocarcinomas is generally unfavorable, whereas the prognosis for intraductal-growing Cholangiocarcinoma is much better (or excellent) after surgical resection [11-14]. Precise characterization of these tumors in terms of their growth pattern and staging is mandatory for optimal treatment planning and for determining a prognosis. Surgical resection should be tailored depending on the morphologic type and the stage of the tumors [10]. In this regard,
the morphologic classification of cholangiocarcinoma is important.
Mass-forming intrahepatic cholangiocarcinoma and infiltrating extrahepatic Cholangiocarcinoma and their imaging findings are well described in the literature [7, 8, 15]; intraductal-growing Cholangiocarcinoma, however, is not. In this review, I describe the gross appearance of intrahepatic and extrahepatic cholangiocarcinomas, correlate the pathologic and imaging findings, consider the mode of spread of these tumors, and discuss the clinical significance of the various growth patterns of cholangiocarcinoma.