Osteopontin (OPN) is an integrin-binding protein, believed to be involved in a variety of physiological cellular functions. The physiology of OPN is best documented in the bone where this secreted adhesive glycoprotein appears to be involved in osteoblast differentiation and bone formation. In our study, we used semi-quantitative RT-PCR of osteopontin in calcification tissue of breast to detect breast cancer metastasis. The obtained data indicate that the expression of osteopontin is related to calcification tissue of breast, and possibly with the incidence of breast cancer. The expression strength of OPN by RT-PCR detection was related to the degree of malignancy of breast lesions, suggesting a close relationship between OPN and breast calcification tissue. The results revealed that expression of OPN mRNA is related to calcification of breast cancer tissue and to the development of breast cancer. Determination of OPN mRNA expression can be expected to be a guide to clinical therapy and prediction of the prognosis of breast cancer patients.