Ex vivo detection of tumoral lymph nodes of colorectal origin with fluorescence imaging after intraoperative intravenous injection of indocyanine green

Background and Objectives The aim of this study was to investigate the potential role of indocyanine green (ICG) fluorescence imaging after intraoperative intravenous (IV) injection for the “ex vivo” detection of metastatic lymph nodes (mLNs) of colorectal cancer origin. Methods Fresh‐fixed LNs in cassettes and/or paraffin‐embedded LNs of patients included in a study that evaluated the role of ICG in the detection of peritoneal metastases of colorectal origin (Protocol NCT‐01995591) were further explored with a dedicated near‐infrared camera system for their fluorescence. An IV injection of ICG was delivered intraoperatively at 0.25 mg/kg. Signal to background ratios (SBRs) were calculated. Results LNs on operative specimens were evaluated for 12 patients (5 males, 7 females). A total of 182 LNs were analyzed. The mean LN number per patient was 15.2 (median: 15.5; range 3–22). SBRs of mLNs were significantly more fluorescent than benign LNs, 1.41 versus 1.04 arbitrary units (P 20 mm2) (P