Its prevalence and incidence are geographically heterogeneous, with the highest rates in Asia, especially Southeast Asia.8 The incidence rate varies significantly between different regions from 5% in Japan to 20% in Korea or even more significant with a 90% incidence in Thailand.9
In high-risk areas in Europe (such as the south of Italy), the incidence is 4.9–7.4/100,000 and 2.9–4.3/100,000 for males and females, respectively. In Crete, Greece, it has increased from 0.998/100,000 in 1992–1994 to 3.327/100,000 in 1998–2000.10
Cholangiocarcinomas are classified according to their anatomic location as intrahepatic and extrahepatic (Table 1). The extrahepatic tumors include those involving the confluence of the right and left hepatic ducts. These account for 80–90%, and the intrahepatic neoplasms represent between 5 and 10% of all cholangiocarcinomas.
Other types include papillary or intestinal type adenocarcinoma, clear cell adenocarcinoma, signet ring cell carcinoma, adenosquamous carcinoma, squamous cell carcinoma, and oat cell carcinoma.11
Extrahepatic cholangiocarcinomas can be subdivided according to the Bismuth classification (Table 2). Other classifications are based on macroscopic appearance of both intra-and extrahepatic tumors (Table 3).