SPARC (osteonectin) in Breast Tumors of Different Histologic Types and Its Role in the Outcome of Invasive Ductal Carcinoma

The purpose of this study was to characterize the immunohistochemical distribution of secreted protein acidic and rich in cystein (SPARC) in benign and malignant breast tumors of different histologic types and define its association with the outcome of invasive ductal carcinoma (IDC) patients. A total of 286 samples of benign and malignant breast lesions between 1994 and 2005 were retrieved from National Taiwan University Hospital. Up to 11 years clinical follow-up data were available for 185 patients with IDC. Immunohistochemistry staining with SPARC was performed in tissue microarray or whole section. The association of expression of SPARC and cumulative overall survival of IDC patients were analyzed using Kaplan-Meier survival analysis and Cox regression analysis. Secreted protein acidic and rich in cystein was not expressed in benign breast phylloides and all benign breast tumors, while expressed in 17.2% of IDC, 85% of metaplastic carcinoma of the breast (MCB), and all malignant breast phylloides. Secreted protein acidic and rich in cystein was strongly expressed in mesenchymal components of MCB and expression levels in epithelial components were variable. The correlation of positive expression of SPARC and poor long-term survival in IDC is significant (p = 0.004). Individuals with positive SPARC expression had 2.34 times higher hazard of death compared with those with negative SPARC expression after adjusting for factors including positive lymph node, TNM tumor stage, estrogen receptor, and progesterone receptor. Secreted protein acidic and rich in cystein may be useful as a prognostic indicator for IDC.