Since the serine protease PMN-E is the only neutral protease that is able to degrade insoluble elastin (Janoff and Schere, 1968; Baugh and Travis, 1976), which is a structural component of breast tissues (Hornebeck et al, 1977), we considered it of interest to study the clinical relevance of PMN-E in breast cancer. Here, ELN is linked to breast cancer.