BACKGROUND Our previous studies demonstrated the expression of procollagen11A1 in fibroblasts of pancreatic cancer desmoplasia and the lack of expression in fibroblasts of pancreatitis by means of the polyclonal antibody (anti-proCOL11A1 pAb) we generated. In a similar way, we decided to compare the expression of procollagen11A1 in fibroblasts of infiltrating ductal carcinoma of the breast and fibroblasts of benign sclerosing lesions of the breast, in order to validate the anti-proCOL11A1 pAb in this setting and to study how proCOL11A1 expression relates to other prognostic and predictive factors, as well as to survival. METHODS 45 core biopsies of sclerosing adenosis and 50 core biopsies of infiltrating ductal carcinoma of the breast were stained with anti-proCOL11A1 pAb, a polyclonal antibody highly specific to the less homologous fraction of proCOL11A1 (in comparison with proCOL5A1 and proCOL11A2). In addition, the expression of the proCOL11A1 gene was measured by RT-qPCR. On the other hand, the expression of proCOL11A1 was compared to the expression of estrogenic receptors, progestagen receptors, the state of the epidermal growth factor receptor 2 (HER2), the histologic grade and the stage of the disease. We also compared the immunohistochemical expression of proCol11A1 to the disease-free interval, and to overall survival. RESULTS The immunohistochemical analysis showed that proCOL11A1 was expressed in 100% of infiltrating ductal carcinomas, but only focally expressed in 2.2% (1 case) of sclerosing adenosis, in agreement with RT-qPCR results. ProCOL11A1 expression did not prove to have a prognostic value in relation to the disease-free interval or to overall survival in infiltrating ductal carcinoma. CONCLUSION The anti-proCOL11A1 pAb is a stromal marker for breast cancer and the expression of proCOL11A1 does not seem to have a prognostic value in infiltrating ductal carcinoma of the breast.