Given the findings that both lipocalin-2 and MMP-9 are mainly secreted into the normal breast ducts and by neutrophils that have infiltrated into the tumor sites [17], we hypothesized that the serum levels of lipocalin-2 and MMP-9 might represent the aggressiveness of breast cancer and might be an independent prognostic factor of breast cancer survival. Here, MMP9 is linked to breast carcinoma.