Compared with stage I–III, stage IV women were more likely to be HER2+/HoR−, HER2+/HoR+, or HER2−/HoR−, and these three subgroups comprised 40% of the patients with metastatic breast cancer while only representing 26% of case patients with stage I–III breast cancer. The gene discussed is ERBB2; the disease is breast carcinoma.