Breast cancer is a heterogeneous disease that is clinically divided into three main subtypes: luminal estrogen receptor (ER)-positive and progesterone receptor (PR)-positive, which are further subdivided into luminal A and B; human epidermal growth factor receptor 2 (HER2)-positive; and triple-negative breast cancer (TNBC). This evidence concerns the gene ERBB2 and triple-negative breast carcinoma.