Introduction The aim of this study was to investigate the prevalence of paraaortic lymph node (LN) metastasis in patients with endometrial cancer, whose preoperative clinical stage was assumed to be FIGO stage l.

Methods We retrospectively analyzed the medical records of 462 patients who underwent surgical staging for endometrial cancer at Yonsei Cancer Center from July 2014 to April 2021. The study population consisted of patients with clinical presumed stage l endometrial cancer and who underwent nodal assessment, including both pelvic and paraaortic LNs.

Results A total of 311 patients met the eligibility criteria for the study. They were classified into low/intermediate and high-risk groups based on histology and myometrial invasion. Of the total patients, 66.9% were classified as low/intermediate risk group, while 33.1% were classified as high-risk group. After surgical staging, 28 patients (9.0%) were upstaged, and 12 patients (3.9%) were found to have LN metastasis. The incidence of LN metastasis was higher in the high-risk group (6.8%) than in the low/intermediate risk group (2.9%). However, the pattern of LN metastasis did not differ between the two groups (pelvic and paraaortic LN metastasis: 16.7% vs. 14.3%; pelvic only: 50% vs. 57.1%; paraaortic only: 33.3% vs. 28.6%, in the low/intermediate vs. high-risk group, respectively).

Conclusion/Implications The incidence of paraaortic LN metastasis in endometrial cancer patients presumed to be FIGO stage l by preoperative radiologic evaluation is low. However, our findings emphasize the importance of nodal assessment, particularly in high-risk groups, as a significant number of patients were upstaged and found to have LN metastasis.