ESR1 and breast cancer: Based on this, the application of immunohistochemical staining techniques has highlighted a great significance in the pathological diagnosis of breast cancer, and the commonly used immunological markers for breast cancer are P63, CK5/6, ER, PR, HER-2, P120, E-cad, EMA, MUC-1, EGFR, Ki-67, P53, and so on.