High-Risk Endometrial Cancer Assessed by Immediate Intraoperative Frozen Sections of Sentinel Lymph Nodes - A Retrospective Study.

While sentinel lymph node (SLN) sampling has been established for low-risk endometrial cancer, few data exists on high-risk histologies. This study aims to measure the accuracy of immediate intraoperative SLN biopsy with frozen section in high-risk endometrial cancer. Patients diagnosed with endometrial cancer of high-grade histology (grade 3 endometrioid, clear cell, serous, carcinosarcoma, de- or undifferentiated histology) between 2014 and 2019 at a single institution who underwent SLN mapping, followed by pelvic lymphadenectomy with or without para-aortic lymphadenectomy were included. SLNs were assessed intraoperatively using multiple frozen sections and H&E staining. Lymph node metastases detected by SLN biopsy were compared with complete lymphadenectomy specimens. 35 patients with high-grade endometrial cancer histology underwent SLN mapping followed by lymphadenectomy. In 34 of 35 (97%) of these patients mapping with at least one SLN was successful. Positive SLNs were identified in 7/34 patients (20.6%). There were no patients who had positive lymph nodes on complete lymphadenectomy without a positive SLN, resulting in 100% sensitivity, and 0% false-negative rate. SLN mapping using intraoperative frozen sections in high-risk endometrial cancer demonstrated 100% sensitivity and 0% false-negative rate, provides immediate feedback on successful SLN mapping and valuable intraoperative information on the disease status guiding the intraoperative decision for completion lymphadenectomy.