However, only 70% of breast cancers express the estrogen receptor (ER), and therefore, chemotherapy and therapies targeting genes with oncogenic alterations and related signaling pathways such as human epidermal growth factor receptor 2 (HER2), epidermal growth factor receptor (EGFR), BRAF, MAP2K1, ALK, CXCR4, etc., have been developed, based on advances in the understanding of molecular cancer biology. This evidence concerns the gene ERBB2 and breast carcinoma.