In multivariate Cox regression analysis, MMP9 mRNA was an independent predictor of BCSS (p = 0.048; HR = 1.3; 95% CI 1.0–1.6) independent of the standard prognostic parameters of BC including tumour size, histological grade, nodal stage, and proliferative fraction as assessed by Ki67. This evidence concerns the gene MKI67 and breast cancer.