- To quantify the relative risk associated with lymphvascular space involvement (LVSI) on outcome measures in patients with apparent stage I endometrial cancer. Six hundred and ninety nine consecutive patients with endometrial carcinoma apparent stage I, who underwent surgery in one of four gynecological oncology centers in Israel, comprised the study population. Forty cases with and 659 without LVSI were followed for a median time of 39 months. Recurrence free, disease specific and overall survival was compared between the two groups. The effect of LVSI, adjusted for other clinical and histo-pathological prognostic factors, was assessed by multivariate analysis. The univariate Kaplan-Meier procedure for survival analysis showed that patients with LVSI had lower recurrence free survival (p=0.0003), worse disease specific (p=0.0007) and overall survival (p<0.0001). Cox proportional hazards model demonstrated a trend toward shorter recurrence free survival (HR=2.0, 95% CI 0.9, 4.5; p=0.08), a worse disease specific survival (HR=2.8, 95% CI 1.1, 7.4; p=0.04) and decreased overall survival (HR=2.0, 95% CI 1.1, 3.8; p=0.03) in cases with LVSI. In patients with apparent stage I endometrial cancer the presence of LVSI, an independent poor prognostic factor, is associated with a two fold increased risk of death. The presence of LVSI warrants consideration when deciding upon post operative management.