Background The 2023 International Federation of Gynecology and Obstetrics (FIGO) staging system includes lymphovascular invasion quantification as a staging criterion for endometrioid endometrial carcinomas; no lymphovascular invasion and focal invasion (≤4 vessels involved) are grouped as one category, and substantial invasion as another.

Objective To assess the association between lymphovascular invasion and oncologic outcomes.

Methods We retrospectively identified patients with FIGO 2009 stage I endometrioid endometrial cancer treated surgically with total hysterectomy and lymph node assessment at two tertiary care centers between January 1, 2012, and December 31, 2019. Lymphovascular space invasion was categorized as focal (<5 vessels involved), substantial (≥5 vessels involved), and no lymphovascular invasion using WHO criteria.

Results Of 1555 patients included, 65 (4.2%) had substantial, 119 (7.7%) had focal, and 1371 (88.2%) had no lymphovascular invasion. Median age was 64 years (range 24–92). Thirty-five patients (53.8%) with substantial, 44 (37%) with focal, and 115 (8.4%) with no lymphovascular invasion had stage IB disease (p<0.001); 21 (32.3%) with substantial, 24 (20.2%) with focal, and 91 (6.6%) with no lymphovascular invasion had grade 3 disease (p<0.001). Thirty-six patients (55.4%) with substantial, 80 (67.2%) with focal, and 207 (15.1%) with no lymphovascular invasion received adjuvant treatment (p<0.001). Median follow-up was 61.5 months (range 0.8–133.9). Five-year progression-free survival rates were 68.7% (substantial), 70.5% (focal), and 90.7% (no invasion) (p<0.001). On multivariate analysis, any lymphovascular invasion was associated with increased risk of progression/death (adjusted HR (aHR)=1.84 (95% CI 1.73 to 1.96) for focal; 2.17 (95% CI 1.96 to 2.39) for substantial). Compared with focal, substantial lymphovascular invasion was associated with an aHR for disease progression of 1.18 (95% CI 1.00 to 1.39).

Conclusions Focal and substantial lymphovascular invasion were associated with increased risk of disease progression and do not appear to be prognostically distinct. Focal versus no lymphovascular invasion have different prognostic outcomes and should not be combined into one category.