Squamous differentiation portends poor prognosis in low and intermediate-risk endometrioid endometrial cancer.

Background: Endometrial cancer presents well-defined risk factors (myometrial invasion, histological subtype, tumor grade, lymphovascular space invasion (LVSI)). Some low and intermediate-risk endometrioid endometrial cancer patients exhibited unexpected outcomes. The aim of this study was to investigate other clinical-pathological factors that might influence the recurrence rates of patients diagnosed with low and intermediate-risk endometrioid endometrial cancer. Methods: A case-control study from a cohort retrospective of 196 patients diagnosed with low and intermediate-risk endometrioid endometrial cancer at a single institution between 2009 and 2014 was conducted. Medical records were reviewed to compare clinical (race, smoking, menopause age, body mass index) and pathological (histological characteristics (endometrioid vs endometrioid with squamous differentiation), tumor differentiation grade, tumor location, endocervical invasion, LVSI) features of patients with recurrence (case) and without recurrence (control) of disease. Three controls for each case were matched for age and staging. Results: Twenty-one patients with recurrence were found (10.7%), of which 14 were stage IA, and 7 were stage IB. In accordance, 63 patients without recurrence were selected as controls. There were no significant differences in any clinical characteristics between cases and controls. Among pathological variables, presence of squamous differentiation (28.6% vs. 4.8%, p=0.007), tumor differentiation grade 2 or 3 (57.1% vs. 30.2%, p=0.037) and presence of endocervical invasion (28.6% vs. 12.7%, p=0.103) were associated with disease recurrence on univariate analysis. On multivariable analysis, only squamous differentiation was a significant risk factor for recurrence (p=0.031). Conclusion: Our data suggest that squamous differentiation may be an adverse prognostic factor in patients with low and intermediate-risk endometrioid endometrial cancer, that showed a 5.6-fold increased risk for recurrence. Keywords: Low and intermediate-risk endometrioid endometrial carcinoma, prognostic factors, squamous differentiation