ObjectiveTo investigate the expression of osteopontin (OPN) in normal breast epithelium, intraductal carcinoma and infiltrating ductal carcinoma and its clinical significance. MethodsThe expression of OPN was examined by SP immunohistochemistry in all specimens, and the results were statistically analyzed. ResultsThe positive rates of OPN in normal breast epithelium, intraductal carcinoma and infiltrating ductal carcinoma specimens were 0%(0/20), 20.0%(5/25) and 43.1%(25/58), respectively, with significant differences found between the latter two groups (P<0.05). OPN expression in breast infiltrating ductal carcinoma was not correlated with the family history, the sizes of primary tumor or patient ages, and it was correlated with histological types, clinical TNM stages and axillary lymphatic metastasis(P<0.05).ConclusionOPN may participate in the development, progression, metastasis of breast cancer, and it may be used for predicting the prognosis of breast cancer.