ERBB2 and breast cancer: This result was reached in a large study: HER2-low in the HR+ group showed higher OS and DFS at 60 months; and the following conclusions were obtained: HER2-low breast cancers showed less aggressive clinicopathologic features compared to HER2–0 cases; and the prognostic impact of HER2-low on resectable breast cancers varied depending on the patient’s HR expression status (23).