Tracer administration
Before injection, the retroperitoneum was opened and lymph node basins were viewed. Withdrawal was first performed to prevent injection into blood vessels, and SLNB was performed by injecting CNS (China Food and Drug Administration approval H20073246; Lai Mei Pharmaceutical Co., Chongqing, China) into the vaginal portion of the cervix at the 3 and 9 o’clock positions. The injection was administered superficially by a skin test needle approximately 5–10 mm from the tumour border and perpendicular to the cervical surface. According to our experience, to achieve better staining, the total volume of the CNS was 0.5 mL, with approximately 0.25 mL administered at each point. The needle was inserted approximately 2–3 mm, and the suspension was slowly injected over the course of approximately 3 min (Figure 1.A). To prevent leakage, the syringe was kept in place for a few seconds after the application. Then, lymphatic drainage of the CNS was observed. The black-stained lymphatic duct resulted in black-stained lymph nodes. SLN was defined as the first lymph node(s) or group of lymph nodes that the CNS drained into, as recognised by black staining through direct visualisation within 15 minutes after completing the injection (Figure 1.B). The time required for SLN mapping was calculated from the time of injection completion to black-staining of the SLN. Subsequently, SLNs were located and removed separately from each side of the pelvis. Hysterectomy with complete pelvic lymphadenectomy was also performed. Adverse reactions were recorded during and after the injection of the tracer. All surgeries were performed by the same experienced surgeons.