Eiro N, Cid S, Fernández B, et al. - Two hundred and forty-six women with invasive breast carcinoma and a long follow-up period were included in this study in order to propose the assessment of matrix metalloproteinase (MMP)-11 expression (also known as stromelysin-3) by intratumoral mononuclear inflammatory cells (MICs) as a beneficial biological marker for breast cancer prognosis. Data reflected the significance of MMP11 and the cellular components of the tumor stroma in breast cancer progression. Results demonstrated that MMP11 expression through stromal cells was significantly related to prognosis. Moreover, MMP11 expression via cancer-associated fibroblasts was correlated with both shortened relapse-free survival (RFS) and overall survival (OS), however, MMP11 expression by MICs exhibited a more robust relationship with both shortened RFS and OS, hence, being the most competent and independent factor to prognosticate RFS and OS.