Our results show that lipocalin-2 is dispensable for tumor development judged by any of the parameters used for determination of the clinical aggressiveness of cancers, such as differentiation grade, time to cancer development, number of mammary glands involved, size of primary tumors, and number and size of metastases in this mouse model of breast cancer induced by the mouse mammary tumor virus-polyoma middle T antigen. This evidence concerns the gene LCN2 and breast cancer.