ERBB2 and breast cancer: Hence, in the present work, we evaluated a large cohort of early breast cancer patients undergoing neoadjuvant chemotherapy to investigate the biological characteristics and pathological complete response to neoadjuvant treatment of HER2-low breast cancer patients, to explore the inconsistency of HER2-low expression from primary breast cancer to matched residual disease, and moreover, to evaluate the influence of HER2-low expression on prognosis.