ERBB2 and breast cancer: In addition, one study (15) found that patients with HR-negative/HER2-positive tumors had more aggressive clinical features, including tumor stages III-IV, T stages 2-4, N stages 1-3, and M stage 1 including brain, liver, and lung metastases, clinical research revealed that BC metastasized mostly to the lung, bone, and liver via circulatory system (16); In contrast, triple positivity was associated with milder tumor behavior.