ERBB2 and breast cancer: A screen from 544 breast cancer patients in The Cancer Genome Atlas (TCGA) database revealed that triple-negative breast tumours express significantly higher levels of miR-138 than luminal tumours, HER2 + tumours, or healthy breast tissue (TNBC: n = 52, luminal: n = 345, TNBC vs luminal p < 0.0001, Fischer’s exact test; Fig. 1A).