Breast HER2 refers to human epidermal growth factor receptor 2 (HER-2) in immunohistochemical detection of breast pathology. HER-2(2+) cannot determine whether HER-2 is positive or not, and it is necessary to carry out ISH test to further clarify HER-2 status. HER-2 is an important prognostic factor for breast cancer, and HER2-positive patients in the state of not receiving standardized treatment generally have a poor prognosis, with shorter disease-free survival and overall survival. At the same time, HER-2 is an important indicator that can predict the response to certain treatments. HER-2 gene amplification or overexpression suggests that the tumor has a lower response to endocrine therapy and CMF regimen chemotherapy, and a higher sensitivity to anthracycline-based chemotherapy. While HER-2(2+) cannot be judged as positive, further ISH testing is needed to clarify the HER2 status to guide the selection of clinical treatment options and predict the prognosis.