Previous studies, like that reported by Qiu et al., reported the negative predictive value of axillary ultrasound in cT ≤ 3 cm, cN0, and Her2-positive tumors to be 78.5% and 89.6% if one lymph node metastasis was considered negative, and 93.3% if one lymph node metastasis was considered negative. This evidence concerns the gene ERBB2 and metastatic malignant neoplasm in the lymph nodes.