A combined four immunohistochemical marker score (IHC4 score), which includes the estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2) and Ki-67, has been clinically validated to evaluate the risk of early distant recurrence in ER+ breast cancer patients [16, 25, 26]. This evidence concerns the gene ERBB2 and breast cancer.