Introduction This study aimed to preoperatively identify high- and low-risk subgroups of patients with lymph node (LN) metastasis in presumed early-stage endometrioid endometrial cancer patients treated with systematic pelvic and para-aortic lymphadenectomy.

Methods Clinicopathologic data of presumed early-stage endometrioid EC patients (N = 361) treated with total hysterectomy with systematic lymphadenectomy between March 2000 and July 2022 were analyzed. None of the patients had definite evidence of LN metastasis in a preoperative magnetic resonance imaging (MRI). Preoperative risk factors including tumor location on MRI for LN metastasis were used to identify variables associated with LN metastasis. Multivariate models were estimated using the backward logistic regression method.

Results LN metastasis was confirmed in 19 patients (5.3%). Cervical stroma invasion on MRI (odds ratio, 4.386; 95% confidence interval, 1.020 – 18.852; P = 0.047), Cornual location on MRI (odds ratio, 36.208; 95% confidence interval, 7.902 – 165.913; P < 0.001), and lower uterine segment/isthmic location on MRI (odds ratio, 8.454; 95% confidence interval, 1.567 – 45.610; P = 0.013) were independent variables for LN metastasis. Patients were categorized into low- and high-risk groups according to risk criteria. Significant differences in the rates of LN metastasis were observed between the groups (0.4% vs. 22.2%, P < 0.001).

Conclusion/Implications A model using tumor location including uterine cornua and lower uterine segment/isthmus was significantly correlated with the risk of LN metastasis. Even in presumed early-stage endometrioid endometrial cancer patients, therefore, tumor location including cornua and isthmus should be investigated to determine whether to perform sentinel LN biopsy or lymphadenectomy.