According to the expression of its estrogen, progesterone, and Her2 receptor, breast cancer can be divided into four subgroups: luminal A-ER positive, PR positive, and Her2 negative; luminal B-ER positive, PR positive, and Her2 positive; Her 2 phenotype-ER negative, PR negative, and Her2 positive; and triple negative phenotype-ER negative, PR negative, and Her2 negative. This evidence concerns the gene ERBB2 and breast cancer.