The value of systematic lymph node dissection for intrahepatic cholangiocarcinoma from the viewpoint of liver lymphatics

Lymph node (LN) metastasis from intrahepatic cholangiocarcinoma (IHCC) might be one of the most important indicators of aggressive surgical resection, yet the value of LN dissection is still controversial. To address this clinical problem, we need to better understand the multidirectional lymphatic outflow from the liver. Although most hepatic lymph flows into the hilar LNs along portal triads, there are also several lymphatic outflows directly communicating with distant areas or the general lymphatic system. Moreover, it has been revealed that LN metastasis spreads to more distal LNs through the hepatoduodenal ligament or other multidirectional lymphatic pathways connected to the general lymphatic system. Therefore, systematic LN dissection might merely be LN sampling in IHCC with LN metastasis. A multidisciplinary strategy focusing on adjuvant treatment after surgery is immediately necessary in these cases. In IHCC without LN metastasis, the accuracy of preoperative imaging assessment of LN metastasis is unsatisfactory and useless for detecting metastatic LNs in clinical settings. Therefore, prophylactic systematic LN dissection for IHCC without preoperative LN swelling is recommended for accurate LN status assessment and reduction of local recurrences. However, this procedure might not offer any clinical benefit according to the results of retrospective comparative studies. In this review, we summarize previous reports regarding lymphatic outflow of the liver and discuss LN dissection for IHCC.