The studies included clinical and experimental research analysing the expression and activity of selected metalloproteinases, including MMP-2, MMP-9, MMP-7 and MMP-1, and pro-inflammatory cytokines such as interleukins (ILs): IL-6, IL-8, IL-17, and IFN-γ in serum, urine, and tumor tissues of patients with BC, using immunochemical methods and genetic analyses. The gene discussed is MMP9; the disease is neoplasm.