Introduction/Background Endometrial intraepithelial neoplasia (EIN) is a precancerous lesion with potential progression to endometrial cancer (EC). The decision to perform sentinel lymph node (SLN) assessment in patients with a preoperative diagnosis of EIN is complex.This study aims to evaluate the utility of SLN assessment, the risk of lymph node involvement and the prevalence of underlying cancer.

Methodology The study was conducted at five Turkish gynecologic oncology institutions enrolling 114 patients with a preoperative diagnosis of EIN. All patients underwent hysterectomy, bilateral salpingectomy, optional oophorectomy, and SLN assessment. The rate of EC and the sensitivity of SLN were calculated.

Results 114 patients included in the study. 48 were diagnosed with EC (42.1%), 42 with EIN (38.6%), and 21 with simple hyperplasia (19.3%).7 of 48 EC patients had high-risk factors including deep myometrial invasion, high-grade disease and lymphatic metastasis. Of the 18 patients with a preoperative diagnosis of EIN with high suspicion for carcinoma, 11 (61.1%) were diagnosed with EC at final pathology. Unilateral SLN detection was 100% of all patients and bilateral SLN node detection rate was 82.4%. Malign SLN detected in 2 patients (4.16%) in EC group. Five patients received adjuvant EBRT, and two underwent chemotherapy combined with brachytherapy and EBRT. 15 patients had an elevated CA125 level ( >35 U/ml) and 9 of them(60%) had a diagnosis of EC .

Conclusion Concomitant EC rate is 42.1% in patients with EIN and the risk increases to 61.1% in patients diagnosed with EIN with high suspicion for carcinoma. 14.5% of the EC (n=7) cases had at least 1 high risk factor for lymphatic metastasis or had lymph node involvement. SLN mapping might be a feasible approach particularly in patients with suspicion for carcinoma on preoperative pathology evaluation and/or elevated CA125 levels to avoid restaging surgery for lymph node status.

Disclosures No disclosure.