Syndecan-1, a cell surface proteoglycan found predominantly on epithelia of mature tissues, binds both extracellular matrix (ECM) components and basic fibroblast growth factor (bFGF) and is implicated in the restriction of growth and invasiveness of neoplastic cells, as it induces the adhesion capacity of neoplastic cells with the stroma. In this study we investigated breast carcinomas for the immunohistochemical expression of syndecan-1 protein and these results were assessed in relation to clinicopathological parameters, in order to clarify its prognostic value. The possible relationship with hormone receptors content, p53, cell proliferation markers, and extracellular matrix components was also estimated. Tissue sections from 102 breast carcinomas were used and immunostainings were performed on formalin-fixed, paraffin-embedded tissue sections by the labelled streptavidin avidin biotin (LSAB) method. High expression levels were observed, as 75/102 (73.5%) cases expressed immunoreactivity in more than 80% of neoplastic cells, while 67/102 (65.7%) exhibited high staining intensity. The survival analysis showed an increased mortality risk associated with high syndecan-1 staining intensity with borderline significance (p=0.041). In addition, there was a strong negative correlation between syndecan-1 protein expression and ECM, specifically collagen IV (p=0.026) and tenascin (p=0.0067). The results of the present study show the implication of this protein in the remodeling of breast cancer tissue, through the interaction with other extracellular matrix components, probably influences the tumour progression.