HER-2(2+) is an immunohistochemical finding in the pathology report of breast cancer. HER-2(2+) means that the expression intensity of HER-2 gene in cancer cells is moderately positive by immunohistochemical staining, which can be considered as critical. Generally speaking, when the immunohistochemistry result is HER-2(2+) in the pathology report of a breast cancer patient, it is not possible to determine whether the patient is HER-2 positive or not, and HER-2(2+) can be considered as critical. In order to further distinguish whether it is positive or not, further FISH testing is done to clarify whether it is amplified or not based on the results of the test in order to develop a subsequent treatment plan. If the FISH test suggests positive gene amplification, it can be judged that the patient is HER-2 positive, and at this time, it is necessary to add trastuzumab for targeted therapy to reduce the recurrence rate. Targeted therapy can reduce the probability of recurrence and metastasis by 50% for HER-2-positive patients, and it can prolong the overall survival for late-stage breast cancer. If the FISH test is negative for gene amplification, then it can be recognized that the patient is HER-2 negative, then there is no need to do trastuzumab targeted therapy, for the indicators of negative patients, the clinical application of targeted drugs can only increase the adverse reactions, can not improve the patient’s prognosis.