Although previous studies on LCN2 have demonstrated conflicting roles as an oncogene or a tumor suppressor gene in multiple malignancies, such as gastric cancer (16, 35, 36), breast cancer (15, 37), ovarian cancer (38), prostate cancer (39), oral squamous cell carcinoma (17), hepatocellular carcinoma (18), cholangiocarcinoma (40) and colorectal cancer (41), research on the tumor metastasis is far from sufficient particularly regarding the underlying mechanisms. This evidence concerns the gene LCN2 and breast cancer.