BC can be divided into three classifications based on marker expression: Luminal A (ER(+) and /or PR(+) and HER2-neu (−)), Luminal B (ER(+) and /or PR(+) and HER2-neu(+)), and Triple Negative (ER(−), PR(−) and HER2-neu (−)). This evidence concerns the gene ERBB2 and breast cancer.