Objective: Laminin is a major glycoprotein component of basement membrance which is an important barrier to tumor cells which must be breeched before metastatic spread can occur. Proteolytic enzymes play an important role in mediating the passage of cancer cells through the basement membrane (BM) and extracellular matrix. We compared the patterns of laminin and cathepsin D (CD) expressions in a range of benign and malignant breast lesions to better understand the process of tumor progression. Methods: One hundred and sixty-two cases of breast samples comprising 18 fibroadeomas, 22 cases of fibrocystic disease, 96 cases of invasive ductal carcinoma and 26 carcinomas with intraductal components were evaluated for laminin and cathepsin D expressions by immunohistochemical staining. Results: The prevalence of CD positivity in both neoplastic and stromal cell components were significantly higher in higher histological grade tumors compared to lower grades (P＜0.001). Various severity of BM disruption correlated with histological grade of the carcinomas (P＜0.001). There was a negative correlation between the laminin expression and CD presence. Conclusion: In the process of cancer cell invasion and metastasis, the basement membrane is disrupted by proteinase secreted by cancer cells, especially by stroma cells of cancer.