Breast cancer requires immunohistochemistry. Breast cancer is a heterogeneous disease with different molecular typing. Immunohistochemistry is used to determine the molecular typing of breast cancer, and common examination indexes include estrogen receptor, progesterone receptor, human epidermal growth factor receptor 2, and tumor proliferation antigen. Molecular typing is closely related to the growth and infiltration of breast cancer tumors, metastasis and recurrence, and provides necessary reference for the selection of subsequent treatment options. For patients with positive estrogen and progesterone receptors, endocrine therapy such as tamoxifen and anastrozole can be applied. For patients with positive human epidermal growth factor receptor 2, targeted therapy is feasible. ki67, as a breast cancer proliferation-associated antigen, the higher its index, the worse the prognosis, and the subsequent treatment needs to be more aggressive. If breast cancer is diagnosed, it is recommended to visit a hospital for diagnosis and treatment under the guidance of a doctor.