['To evaluate whether the presence of mucinous differentiation influences histopathologic findings, stage distribution, or rate of recurrence among women with grade 1, endometrioid type, endometrial carcinoma.', 'This was a retrospective cohort study of all patients with grade 1, endometrioid type, endometrial carcinoma between January 2005 and December 2012. Patients were separated by the presence or absence of mucinous differentiation and then compared.', 'Of 655 patients, mucinous differentiation was present in 137 (20.9%) and absent in 518 (79.1%) patients. Compared to the group without mucinous differentiation, the group containing mucinous differentiation was older at diagnosis (mean: 61.1 vs. 58.5 years, OR, 95% CI; 1.03, 1.01-1.05) and more likely to have myometrial invasion (61.3% vs. 51.5%, OR, 95% CI; 1.49, 1.01-2.19). Additional histopathologic findings including: tumor size, cervical stromal invasion, adnexal involvement, LVI and/or the presence of positive lymph nodes were similar between groups. Mucinous differentiation did not affect stage distribution, as most patients were stage 1A (85.4% vs. 86.3%). The median PFS for the entire group has yet to be reached. The mean PFS for the entire study sample was 94.7 months. There was no difference in mean PFS when comparing the group with mucinous differentiation to the group without mucinous differentiation (98 vs. 93.4 months, p=0.07).'] Does mucinous differentiation impact stage or risk of recurrence among patients with grade 1 , endometrioid type , endometrial carcinoma?