Vascularity of Intrahepatic Cholangiocarcinoma on Computed Tomography is Predictive of Lymph Node Metastasis

The indications for lymph node dissection (LND) for intrahepatic cholangiocarcinoma (ICC) are controversial. Seventy patients with mass-forming dominant ICC underwent hepatectomy with systematic LND or lymph node sampling between 2003 and 2013. We defined the computed tomography (CT) ratio as the CT value (Hounsfield units) of the tumor divided by the CT value (Hounsfield units) of the liver parenchyma in the late arterial phase, and investigated the indications for LND with hepatectomy for ICC. A multivariate analysis identified lymph node metastasis (LNM; n = 19, p = 0.012) and perineural invasion (p = 0.017) as independent predictors of survival. The median survival time and 5-year survival rate in patients exhibiting LNM were 31.1 months and 16.0 %, respectively. In a subgroup analysis of patients without LNM, overall survival was comparable between patients treated with LND and those treated without LND (p = 0.801). A multivariate analysis of the preoperatively measurable parameters revealed that a CT ratio < 0.88 and macroscopic periductal infiltration were independently associated with LNM. We developed a score predicting LNM of mass-forming dominant ICC (LMIC score), assigning 1 point for each of these risk factors. The percentages of patients with LNM with an LMIC score of 0, 1, or 2 points were 0, 35, and 58 %, respectively. The vascularity of ICC is associated with important prognostic factors, LNM, and perineural invasion. LN dissection would be conducted in patients with an LMIC score of one or two points but can be omitted in patients with an LMIC score of zero.