These cases, representing about 40% of ER-negative/HER2-negative breast cancers in this cohort, displayed down-regulated mRNA expression of adhesion molecules claudin 3, claudin 4, claudin 7, E cadherin and occludin compared with basal ER-negative/HER2-negative breast cancers and luminal A, ER-positive/HER2-negative breast cancers (Figure 1A–C). This evidence concerns the gene ERBB2 and breast cancer.