Several studies have described the role of MMPs in breast cancer progression and metastasis development, as MMPs are involved in the degradation of basement membranes.23 In a meta-analysis24 including more than 10,000 cancer cases, MMP-9(1562 C/T) was shown to increase the risk of cancer metastasis, correlating the polymorphism with a more aggressive disease (OR = 1.25, IC95: 1.03 - 1.51, p = 0.07). Here, MMP9 is linked to breast cancer.