Breast cancer refers to malignant tumors originating from the glandular epithelium of the breast, and FISH test is a fluorescence in situ hybridization detection method. If the HER2 gene test is 0 or 1 plus sign, it is judged as negative and should not be treated with targeted drugs; if the HER2 gene test is 2 plus signs, FISH test is needed to determine the negative and positive. positive HER2 gene test is one of the adverse factors affecting the prognosis of patients, and can be treated with targeted therapy using trastuzumab, and most of the patients’ cure rate and survival can be the same as that of the patients with negative HER2 gene test. Most patients can be treated with trastuzumab.