These findings consistently demonstrate a clear association between HER2-positive tumors and AA, Asian, and Latina ethnicities, suggesting the presence of disparities in the distribution of breast cancer subtypes among minority groups in the U.S. However, it is important to note that breast tumor subtype classification is often conducted based on the IHC expression of ER, PR and HER2 biomarkers (42). This evidence concerns the gene ESR1 and breast cancer.