Extracellular matrix metalloproteinase inducer (EMMPRIN) is a member of the immunoglobulin superfamily of adhesion molecules and has a role in the activation of several matrix metalloproteinases (MMPs). We evaluated whether EMMPRIN expression is related to tumor progression and patient outcome in human endometrial carcinoma. Paraffin-embedded surgical tissue samples from 112 patients with endometrial carcinoma were stained with anti-EMMPRIN antibody (monoclonal antibody 12C3:MoAb 12C3) for immunohistochemical analysis. EMMPRIN protein was expressed in cancerous lesions with the incidence of 97.3% (109 of 112 cases), but not in normal lesions. The scores determined by the combination of intensity and pattern of EMMPRIN staining in cancer cells correlated significantly with various histopathological risk factors: advanced stage, P=0.001; poorly differentiated carcinoma, P<0.001; lymph node metastasis, P=0.002; and lymphatic vessel infiltration, P=0.027. More importantly, recurrence-free survival was shortened in patients with higher EMMPRIN scores (HR, 3.08; 95% CI, 1.32-7.19; P=0.01). These results suggest that measurement of EMMPRIN expression with simple immunohistochemical staining may enhance the understanding of the pathophysiology of endometrial carcinoma.