Impact of lymphovascular space invasion on lymph node metastasis in low-grade endometrial cancer with shallow myometrial invasion and negative imaging.

Background: This study aimed to determine the frequency of lymph node metastasis in endometrioid carcinomas of grades 1 or 2 with shallow myometrial invasion and lymphovascular space invasion (LVSI). Methods: After obtaining institutional review board approval, we retrospectively reviewed the medical records of 133 patients with endometrial cancer who were treated at our hospital between January 2007 and December 2022. These patients met the following criteria: endometrioid carcinoma grade 1 or 2, myometrial invasion less than 50%, and preoperative CT showing regional lymph nodes with a short diameter less than 10 mm. All patients underwent pelvic and para-aortic lymphadenectomies. Results: Lymph node metastasis was identified in 10 (8%) cases. LVSI was significantly associated with lymph node metastasis (odds ratio 8.278, 95% CI 2.239–32.035, P-value: 0.002). LVSI was present in 32 (24%) of the 133 cases, and among these, 7 (22%) had lymph node metastasis. Of the patients with lymph node involvement, 3 (44%) had only pelvic metastases, 2 (28%) had only para-aortic metastases, and 2 (28%) had both pelvic and para-aortic metastases. All patients received postoperative adjuvant chemotherapy, and there were no recurrences or deaths during the study period among those with lymph node involvement. Conclusion: Even in endometrioid carcinoma grade 1–2 with shallow myometrial invasion, where lymph node metastasis is not suspected on imaging, the presence of LVSI may be a crucial factor in deciding whether to perform subsequent lymphadenectomy.