The expression of HR in combination with human epidermal growth factor 2 (HER2) is clinically used to classify breast cancer into four biomarker profiles or subtypes as follows: HR+HER2–, HR+HER2+, HR–HER2+, HR–HER2– (also known as triple-negative breast cancer or TNBC). This evidence concerns the gene ERBB2 and breast carcinoma.