Research on the clinical characteristics and prognostic impact of HER2 low expression in breast cancer subtypes has been conducted, with studies examining its effects in various types of breast cancer, including triple-negative and HER2-negative cases. The studies have investigated factors such as tumor-infiltrating lymphocytes, estrogen receptor expression levels, and epigenetic determinants, and their impact on patient outcomes. The findings appear to be part of a broader effort to understand the prognostic implications of HER2 low expression in breast cancer, with data drawn from real-world cohorts and various patient populations.