Two-step sentinel lymph node mapping strategy in endometrial cancer staging using fluorescent imaging: A novel sentinel lymph node tracer injection procedure

Objective: The current sentinel lymph node (SLN) tracer injection procedure for endometrial cancer commonly uses cervical injection, which can detect SLNs of the uterine cervix but not the uterine body. This study describes an SLN tracer injection procedure, titled two-step SLN mapping, which can identify SLNs of the uterine body and cervix using fluorescent imaging with indocyanine green (ICG) and results of SLN biopsy. Methods: In 50 consecutive patients with endometrial cancer, two-step SLN mapping was performed during laparoscopic surgical staging with the PINPOINT real-time fluorescence imaging system. The first step was to identify SLNs of the uterine body. In total, 4-6 mL of ICG was injected into the bilateral uterine cornual areas, and lymphatic channels were traced, followed by identification and removal of paraaortic SLNs. The second step was to identify SLNs of the uterine cervix by injecting 4 mL of ICG into the cervix. After harvesting the mapped pelvic SLNs, complete pelvic and paraaortic lymphadenectomy was performed to validate the two-step SLN mapping strategy. Results: Our two-step SLN mapping strategy produced excellent SLN detection rates: 100% (50/50) overall for SLNs; 98.0% (49/50) for pelvic SLNs; 94.0% (47/50) for bilateral SLNs; and 86.0% (43/50) for paraaortic SLNs. We detected microscopic metastasis in harvested SLNs of 4 patients (8.0%). The sensitivity, specificity, and negative predictive value of SLN detection were all 100%. There was no false negative case. Conclusion: The two-step SLN mapping strategy to identify lymph nodes from the uterine fundus and cervix was feasible. This strategy could be more accurate in identifying paraaortic lymph node metastasis than the cervical injection method.