Sentinel Lymph Node Mapping of Liver

Background Although the sentinel lymph node (SLN) hypothesis has been applied to many tissues and organs, liver has remained unstudied. Currently, it is unclear whether hepatic SLNs even exist. If so, they could alter the management of intrahepatic cholangiocarcinoma and other hepatic malignancies by minimizing the extent of surgery while still providing precise nodal staging. This study investigated whether invisible yet tissue-penetrating near-infrared (NIR) fluorescent light can provide simultaneous identification of both the SLN and all other regional lymph nodes (RLNs) in the liver. Methods In 25 Yorkshire pigs, this study determined whether SLNs exist in liver and compared the effectiveness of two clinically available NIR fluorophores [methylene blue and indocyanine green (ICG)], and two novel NIR fluorophores previously described by our group (ESNF14 and ZW800-3C) for SLN and RLN mapping. Results In this study, ESNF14 showed the highest signal-to-background ratio and the longest retention time in SLNs without leakage to second-tier lymph nodes. The findings showed that ICG had apparent leakage to second-tier nodes, and ZW800-3C had poor migration after intraparenchymal injection. However, when injected intravenously, ZW800-3C was able to highlight all RLNs in liver during a 4- to 6-h period. Simultaneous dual-channel imaging of SLN (ESNF14) and RLN (ZW800-3C) permitted unambiguous identification and image-guided resection of SLNs and RLNs in liver. Conclusion The NIR imaging technology enables real-time intraoperative identification of SLNs and RLNs in the liver of swine. If these results are confirmed in patients, new strategies for the surgical management of intrahepatic malignancies should be possible.