Although based on a small number of cases, this analysis revealed that the genes recurrently altered in metastatic mixed mucinous BC and not altered in primary mixed mucinous BCs of this study, and pure/ mixed mucinous BCs reported by our group and others15,16,32 included ESR1 (60% vs 0%, respectively; P = 1 × 10−2) and NCOR (40% vs 0%, respectively; P = 6 × 10−2; Fig. 2c). Here, ESR1 is linked to breast cancer.