Purpose: It was speculated that intrahepatic cholangiocarcinoma (ICC) invasion would influence cancer progression, such as lymph node (LN) metastasis, and the efficacy of LN dissection (LND). The purpose of this study is to evaluate the LN metastatic pattern of intrahepatic cholangiocarcinoma, including the invasion category and prognosis after surgical resection, in order to explore effective LND. Methods: We analyzed a prospectively collected cohort for ICC with a previously reported invasion category: hilar type, showing invasion to the main or first branch of Glisson; peripheral type, showing no invasion to less than the third branch; and intermediate type, for all others. Results: Data from a total of 180 patients who underwent surgical resection were analyzed (LN dissection in 142 (79%)). In single ICC, hilar type had a higher LN metastatic rate than the others (hilar; 23/45 (51%), intermediate; 7/25 (28%), peripheral; 1/34 (3%)). Although the survival with LN metastasis (LN+) was worse, single and hilar/intermediate ICC LN+ had a better survival than peripheral type LN+ (3-year OS: hilar/intermediate 30–37%, peripheral 0%). The most frequent LN metastatic region was the hepatico-duodenal ligament for all invasion categories, and the LN metastatic region was not related to the survival. In peripheral ICC, LND did not affect the survival. By contrast, hilar/intermediate ICC LN+ had a better survival than did peripheral ICC LN+, and the 3-year OS was ≥ 20%. Conclusion: LN metastasis depended on the ICC invasion category in addition to the tumor number, which affected patients’ survival and the need for LND. In hilar-type disease, LN dissection may contribute to the survival.
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