In a previous study using tissue microarray containing samples from 207 breast cancer patients, elevated expression of lipocalin-2 correlates with some indicators of a phenotype severity including a low ER/PR expression, a low grade of differentiation, the presence of lymph-node metastases and a high Ki-67 proliferation index, and overexpressed lipocalin-2 is associated with poor DFS consistent with our results using serum [17,28,29]. Here, ESR1 is linked to breast cancer.