After adjusting for age, menopausal status, histological subtype, tumor size, grading, lymphovascular invasion, receptor status, HER2 status, mastectomy and NC, the multivariate Poisson regression analysis confirmed neoadjuvant treatment as the strongest independent factor for a lower LNY after ALND (p < 0.0001). The gene discussed is ERBB2; the disease is neoplasm.