The secretion of matrix metalloproteinases (MMPs) is crucial in the metastasis of cancer cells, since MMPs are responsible for the degradation of extracellular matrix (ECM). Among them, matrix metalloproteinase-7 (MMP-7) or matrilysin 1 is a stromelysin which degrades type-IV collagen, fibronectin and laminin. Immunohistochemistry was performed to detect MMP-7 protein in infiltrative breast carcinomas. MMP-7 was studied along with clinicopathological parameters, disease-free and overall survival, and p53, c-erbB-2, topoIIa, MMP-2, uPAR and beta-catenin. MMP-7 immunoreactivity was detected in the cytoplasm of cancer cells in 54.2% (96/177) and tumor stromal cells in 47.5% (84/177), as well as in normal epithelium adjacent to malignant epithelium. MMP-7 reactivity in cancer cells displayed an inverse association with nuclear grade (p=0.049) and topoIIa (p=0.03). A parallel association was observed between the expression of MMP-7 in both malignant and stromal cells with uPAR in cancer cells (p=0.033 and p=0.027, respectively). MMP-7 of tumor stromal cells depicted a parallel correlation with MMP-2 of the same cell type (p=0.044), while abnormal beta-catenin expression was inversely associated with MMP-7 of cancer cells (p=0.047). Our results show the multifunctional role of MMP-7 in the mammary gland, since it seems to be associated with a less aggressive phenotype, while, at the same time, being involved in invasion, through its collaboration with indicators of invasion.