Since the genetic background influences the development of tumor growth and metastasis in MMTV-PyMT transgenic mice, we chose to use highly inbred mice from the FVB/N strain and heterozygous breeding to generate minimal genetic variation in order to detect even minor effects of lipocalin-2 in cancer development, a model that has been very useful in previous studies [35]–[37]. The gene discussed is LCN2; the disease is neoplasm.