Based on an estimating model, the aim of our study was to evaluate the axillary lymph node involvement of patients with primary invasive early human epidermal growth factor receptor 2 (HER2)-positive breast cancer before receiving neoadjuvant therapy (NAT). Patients with primary surgery (n = 63) were compared with patients who had received NAT (combined chemo/HER2-targeted antibody therapy) before surgery (n = 152). In patients receiving NAT, a positive N stage was estimated in 73.2 (49.8%) tumors resulting in a conversion (positive N stage-ypNpositive) of 35.5%. In 126 cases with ypN0 stage, a positive N stage was estimated in 41.4%.
Keywords: HER2-positive breast cancer; axillary response; estimating model; neoadjuvant therapy; pathological node stage.