Association between human epidermal growth factor receptor 2 status, namely low and zero expression, and prognosis in hormone receptor-positive breast cancer: a single-center retrospective study.

We inferred that the HER2-low and HER2-zero statuses do not affect the RFS and OS of patients with ER-positive breast cancer. The prognostic significance of HER2-low or HER2-zero status in luminal A- and B-like breast cancers might differ, and a new treatment strategy is required for the HER2-low subgroup.