Endometrial Cancer with and without Endometriosis: Clinicopathological Differences

Endometriosis is known to be associated with an increased risk of endometrioid and clear cell ovarian cancer. However, the association between endometriosis and endometrial cancer is controversial. Therefore, we retrospectively analyzed the medical records of women with endometrial cancer who had undergone surgery at our institution to evaluate the clinicopathological relationship between endometrial cancer and endometriosis. The study included 720 women pathologically diagnosed with endometrial cancer at our hospital between 2000 and 2020. The participants were allocated to two groups of patients with endometrial cancer: patients with endometriosis (n = 101) and patients without endometriosis (n = 619). Endometrial cancer patients with endometriosis were significantly younger (median age 54.0 vs. 58.0; p = 0.002). In addition, endometrial cancer patients with endometriosis had fewer pregnancies and deliveries (median pregnancy 1.58 vs. 1.99; p = 0.019, median delivery 1.25 vs. 1.56; p = 0.012). The percentage of patients classified as stage IA was significantly higher in those with endometrial cancer with endometriosis (68.3% vs. 56.4%; p = 0.029). In the analysis of synchronous ovarian cancer, the percentage of dual primary cancer was higher in patients with endometriosis (14.9% vs. 1.6%; p < 0.001). The association of young-onset early-stage endometrial cancer with endometriosis is an important finding that cannot be ignored clinically.