Immunohistochemistry is an important adjunct in pathological diagnosis. Generally, if immunohistochemistry is requested after routine pathological examination, it is mainly used for the following purposes: 1. to further determine the nature of lesions as benign or malignant: some benign and malignant lesions are difficult to diagnose under ordinary pathological sections, so immunohistochemistry is needed to solve the problem in order to guide the next treatment plan; 2. to determine the origin of metastatic tumors: through immunohistochemical detection of tumor The specific antibodies expressed by tumor cells can help to identify the real source of the cells and can help to determine the organ of origin of the tumor; 3. Further pathological typing of a certain type of tumor: different pathological types of a certain disease have different degrees of benignity and malignancy, so the prognosis is different, and the treatment methods are certainly different. Therefore, a group of immunohistochemistry is needed for the final comprehensive analysis to clarify the tumor type. 4. Immunohistochemistry can help to detect tiny metastases: sometimes there are only a few cancer cells among tens of thousands of lymphocytes in lymph nodes, which is difficult for doctors to detect if they only rely on the conventional H-E pathological sections. Immunohistochemical detection will help to determine the clinical treatment plan, including the scope of surgery; 5. For judging the prognosis as well as guiding the treatment: more common breast cancer treatment, immunohistochemistry of ER, PR, HER-2 and Ki-67 is needed in breast cancer specimens, which can guide the next treatment plan of breast cancer as well as judging the patient’s prognosis.