Lymphatic spread from left-sided intrahepatic cholangiocarcinoma: reconsiderations based on the lymphatic drainage from the liver

Intrahepatic cholangiocarcinoma (ICC) is known to have a high frequency of lymph node metastasis. Lymph node dissection (LND) is recommended for accurate staging, but the survival benefit of LND remains unclear. Knowledge of the pathways and direction of lymphatic drainage to the regional lymph nodes is essential when considering LND to improve patient survival. The liver has three lymphatic drainage pathways: portal, sublobular, and subcapsular. Of these, the portal lymphatic pathway, which lies along with the portal tracts, is the primary pathway. The efferent portal lymphatic vessels from the left-sided liver, which continue from the portal lymphatic pathway of the liver, communicate with the lymphatic vessels and lymph nodes along the hepatic artery at the hepatoduodenal ligament. In addition, lymphatic flow may also present along the left embryonic (aberrant) hepatic artery in the lesser omentum, based on our experience. This pathway is the previously reported pathway from the left-sided ICC to the lesser curvature of the stomach. However, through this pathway, ICC cells reach lymph nodes along the root of the left gastric artery but not the perigastric lymph nodes along the lesser curvature because of the opposite direction of lymph flow. Although further analyses using a large number of cases are needed to confirm these observations, these two pathways, along the hepatic artery at the hepatoduodenal ligament and the left embryonic (aberrant) hepatic artery in the lesser omentum should be considered when performing LND in the case of ICC in the left-sided liver.