Endometrial stripe thickness: a preoperative marker to identify patients with endometrial intraepithelial neoplasia who may benefit from sentinel lymph node mapping and biopsy

Objectives The goal of our study was to identify preoperative factors in patients with endometrial intraepithelial neoplasia that are associated with concurrent endometrial cancer to select patients who may benefit from sentinel lymph node (SLN) assessment at the time of hysterectomy. Methods Retrospective single institution cohort study of patients with a preoperative diagnosis of endometrial intraepithelial neoplasia who underwent hysterectomy with or without staging from January 2010 to July 2020. Modified Poisson regression was used to calculate risk ratios (RR) and 95% confidence intervals (CI). Results Of 378 patients with a preoperative diagnosis of endometrial intraepithelial neoplasia, 275 (73%) had endometrial intraepithelial neoplasia and 103 (27%) had invasive cancer on final pathology. Age (p=0.003), race (p=0.02), and hypertension (p=0.02) were significantly associated with concurrent endometrial cancer. The median preoperative endometrial stripe was significantly greater in the endometrial cancer group (14 mm (range 10-19)) than in the endometrial intraepithelial neoplasia group (11 mm (range 8-16); p=0.002). A preoperative endometrial stripe >= 20 mm was associated with double the risk of endometrial cancer on final pathology (crude RR 2.0, 95% CI 1.3 to 2.9) and preoperative endometrial stripe >= 15 mm was 2.5 times more likely to be associated with high risk Mayo criteria on final pathology (crude RR 2.5, 95% CI 1.2 to 5.2). Of those with concurrent endometrial cancer, 5% were stage IB, 29% had tumors >2 cm, and 1% had grade 3 histology. Only 3% of all patients underwent lymph node evaluation. Conclusions In a large cohort of patients with a preoperative diagnosis of endometrial intraepithelial neoplasia, less than a third had invasive cancer and even fewer had pathologic features considered high risk for nodal metastasis, arguing against the use of routine SLN dissection in these patients. Endometrial stripe >= 15 mm may be a useful preoperative marker to identify patients at higher risk for concurrent endometrial cancer and may be an important criterion for use of selective SLN dissection in carefully selected patients with endometrial intraepithelial neoplasia.