ERBB2 and breast cancer: Furthermore, the field also faces several practical problems: a) The efficacy of CAR-T cell clinical trials in breast cancer remains generally limited, and the successes observed in the treatment of hematological malignancies have not been replicated; b) The field has suffered major safety setbacks, especially the fatal acute lung injury in the early HER2-CAR-T cell test (6); c) CAR-T cell therapy for breast cancer also encounters competition from emerging immunotherapies, which may influence its clinical positioning.