To explore the genetic background of patients with HER2 positive breast cancer that benefit from trastuzumab combined with neoadjuvant chemotherapy, identify clinically actionable mutations that associated with trastuzumab resistance or drug efficacy, we designed this Observational phase II trial. The primary endpoint is genetic profile of HER2+ breast cancer patients treated with trastuzumab combined neoadjuvant chemotherapy. Secondary endpoints included pathological complete response (pCR) rate and safety.