Introduction:Cyclooxygenase-2 (COX-2) is a well-known enzyme that promotes tumor growth and metastasis. Cyclooxygenase-2 is upregulated in a number of human epithelial tumors, but data about the significance of COX-2 in mesenchymal tumors are lacking. The purpose of this study was to determine COX-2 expression in uterine sarcomas and whether a relationship exists between COX-2 expression and clinicopathologic outcomes.Methods:Immunohistochemical staining for COX-2 was performed on paraffin-embedded tissue blocks of 49 uterine sarcomas (30 leiomyosarcomas, 14 endometrial stromal sarcomas, and 5 carcinosarcomas). Positive staining was defined as moderate or strong staining in 5% or more of tumor cells.Results:Four of 30 leiomyosarcomas, 1 of 14 endometrial stromal sarcomas, and 2 of 5 carcinosarcomas were positive for COX-2 expression. In leiomyosarcomas, COX-2 expression correlated with tumor stage with marginal significance (P = 0.058). Patients with leiomyosarcoma positive for COX-2 expression had a lower overall survival rate than those without COX-2 expression (P = 0.025). In the multivariate Cox proportional hazards regression model, COX-2 expression, tumor stage, and mitotic count were independently associated with overall survival in leiomyosarcomas.Conclusions:Our data suggest that immunohistochemically determined COX-2 expression is an independent prognostic factor in uterine leiomyosarcomas. Assessment of COX-2 status might be useful for determining the prognosis in patients with uterine leiomyosarcomas.