Molecularly targeted tumor therapy is a therapeutic modality that uses specific genes or expression products of genes expressed by tumor cells with little or no expression by normal cells as therapeutic targets to maximize the killing of tumor cells with less killing of normal cells. Human epidermal growth factor receptor 2 (Her-2) is a clear prognostic indicator for breast cancer and a predictor of the efficacy of targeted drug therapy. As the first humanized monoclonal antibody targeting Her-2, the introduction of trastuzumab (Herceptin) drug has changed the prognosis of Her-2-positive breast cancer patients, influenced the diagnosis and treatment pattern of breast cancer, and is an important breakthrough in breast cancer drug therapy. Therefore, it is important to correctly detect and judge the results of Her-2. Here is a brief introduction of the standard Her-2 test and result determination: 1. Targeted Her-2 drugs are only suitable for Her-2-positive breast cancer patients. 2.Her-2 positive can be defined as standard immunohistochemistry (IHC) ++++, or fluorescence in situ hybridization (FISH) positive. 3.If the patient’s immunohistochemistry test shows Her-2(+++), it can be directly judged as Her-2 positive. If immunohistochemistry test Her-2 (++), FISH test should be performed again for clear judgment. If standard laboratory immunohistochemistry test results Her-2 (+) or Her-2 (-), it is judged as Her-2 negative. 4, Her-2 positive determination can also be done by FISH test. FISH test performed in a qualified laboratory with a ratio greater than 2.2 can be judged as Her-2 positive; less than 1.8 is a Her-2 negative patient; if the result obtained is between 1.8 and 2.2, it should be combined with immunohistochemistry results. 5. If the patient’s disease development does not conform to the characteristics of Her-2 negative patients, the clinical opinion is that it is possible to be Her-2 positive, or recurrent metastatic patients in the treatment process in order to strive for treatment opportunities, it is recommended to conduct Her-2 detection from the beginning, which can use the primary tumor specimen, but more advocate the use of recurrent lesion re-biopsy, the method can use immunohistochemistry or FISH detection.