ERBB2 and breast neoplasm: In HER2-positive breast cancer, the following factors were significantly associated with achieving ypN0 after NAT: post-NAT maximum tumor diameter, tumor remission rate post-NAT, peritumoral echogenicity post-NAT and changes in posterior echogenicity pre- and post-NAT, tumor CDFI signal patterns pre- to post-NAT, minimal transverse lymph node diameter post-NAT, lymph node remission rate post-NAT, visibility of hyperechoic medulla in axillary lymph nodes post-NAT and therapeutic response evaluation of the primary breast tumor (Table 4).