Immediate intraoperative sentinel lymph node analysis by frozen section is predictive of lymph node metastasis in endometrial cancer

Sentinel lymph nodes sampling (SLN) in endometrial cancer is being evaluated as a means to gather prognostic information about lymphatic metastasis while avoiding the morbidity associated with complete lymphadenectomy. SLN ultrastaging has been advocated to identify low-volume metastases, but its value remains uncertain. This study aims to evaluate a pathological protocol for the immediate intraoperative SLN work-up using H&E staining alone. In this retrospective single-center study, patients received standardized cervical injection of indocyanine green, SLN mapping followed by pelvic lymphadenectomy with or without para-aortic lymphadenectomy. SLNs were entirely frozen, multiple H&E stained sections prepared and evaluated intraoperatively. No immunohistochemistry was performed. SLN results were compared with the complete lymphadenectomy specimen. Over 3.5 years, 90 patients were identified who underwent SLN mapping and subsequent complete pelvic lymphadenectomy. At least one SLN was detected in 79 (88%) patients. The median number of SLNs removed was 2.0. Para-aortic SLNs were detected in 7%. Final pathology showed 67% Type I tumors, 76% locally confined. The mean number of lymph nodes removed during complete lymphadenectomy was 21. In this series, only 6 patients had lymph node metastases. 5/6 were identified by the described SLN approach resulting in 83.3% sensitivity and a negative predictive value of 98.7%. Our approach permits immediate intraoperative results and helps guide the primary surgery. The immediate SLN work-up using frozen sections showed both high accuracy and negative predictive value. The comparably lower sensitivity may be related to the low number of patients with positive lymph nodes (7.6%).