Immunohistochemistry may be used to check for cancer, mainly to determine the type of cancerous tumor, and possibly to identify benign tumors. It is a pathological test that is mainly used to identify benign, malignant and malignant tumors as an indicator to determine the type of tumor. For example, if the immunohistochemistry of breast cancer is positive for estrogen and progesterone receptors, it can further guide the subsequent use of drugs for endocrine therapy. If HER2 indicator, that is, human epidermal growth factor receptor-2, is positive (3+) it means that there is excessive amplification, and Herceptin can be continued to be used as a targeted therapy. In addition to identifying benign and malignant tumors, immunohistochemistry can also determine the type of tumor and whether it is suitable for endocrine therapy and targeted therapy, etc., which can guide the subsequent treatment.