Study objective: To determine the anatomical distribution of sentinel lymph nodes (SLNs), the overall, unilateral, and bilateral detection rates, and the bilateral SLN concordance in patients with endometrial cancer (EC) mapped through a retroperitoneal transvaginal natural orifice transluminal endoscopic surgery (vNOTES) approach.

Design: Prospective single-center observational study.

Setting: Swiss teaching hospital.

Patients: Patients with EC or endometrial complex atypical hyperplasia who had undergone surgical staging with SLN mapping by a retroperitoneal vNOTES approach between October 2021 and November 2023.

Interventions: Patients were placed in a horizontal dorsal lithotomy position under general anesthesia, and indocyanine green (ICG) was injected into the cervix. Access to the retroperitoneal space was achieved through vaginal incisions. A 7 cm GelPoint V-Path Transvaginal Access Platform was used as a vNOTES port, and CO₂ was insufflated to expand the retroperitoneal space. The pelvic retroperitoneal space was inspected for ICG uptake by lymph nodes. After identification, SLNs were removed and sent for definitive histological examination.

Measurement and main results: A total of 34 patients were included in this study; 33 (97.1%) had a successful procedure (unilateral or bilateral mapping), and 1 (2.9%) had failed mapping. A total of 124 SLNs were identified and removed. SLNs were observed in the obturator region (81.5%), the external iliac region (10.5%), the internal iliac region (4.8%), and the common iliac region (3.2%). Similar proportions were observed on both pelvic sides. No SLNs were detected in other regions. The SLN locations were symmetrical in 22/31 (71.0%) patients. SLNs were negatives in 120 cases (96.8%), while 2 lymph nodes (1.6%) presented isolated tumor cells, and 2 others (1.6%) presented macrometastases.

Conclusion: We report anatomical distributions and detection rates for SLNs mapped by retroperitoneal vNOTES. Our results suggest substantial differences in the localization of SLNs compared to those reported for laparoscopic mapping.