Immunohistochemistry for breast cancer involves the following aspects: 1. It is used to carry out diagnostic indicators, such as P63 and calponin These two indicators are often used to identify the presence of myoepithelium in the lesioned tissue. If the cells show certain heterogeneity and myoepithelial disappearance, cancer is considered. Generally, e-cadherin is positive in non-specific invasive carcinoma, but not in lobular carcinoma. e-cadherin is generally positive in non-specific invasive carcinoma, but P120 is positive in invasive lobular carcinoma. 2. er, pr, Her-2 and ki67 are four indicators that are routinely tested by immunohistochemistry for breast cancer and are the basis for treatment guidance. If er and pr are positive, endocrine therapy can be performed. If Her-2 is positive, that is, immunohistochemistry ++ is considered positive, so that targeted therapy with Herceptin, Paget, etc. can be carried out directly. ki67 is the judgment of positive prognostic index.