Increasing incidence of intrahepatic cholangiocarcinoma and its relationship to chronic viral hepatitis.

Primary liver cancer is the sixth most common cancer and third most common cause of cancer death worldwide. Cholangiocarcinoma is the second most common primary liver tumor after hepatocellular carcinoma. Because the incidence of intrahepatic cholangiocarcinoma is rising in most areas worldwide, identification of the main causes of this problem is urgently needed. Despite well-known risk factors in the development of intrahepatic cholangiocarcinoma, recent reports focus on chronic hepatitis B and C viral infections because an increasing number of studies have observed an association. The relationship, however, is still not conclusive because of the diversity in clinical reports and the lack of in vitro evidences. This issue should be emphasized and further investigation is required for clarification.