ERBB2 and breast cancer: According to the breast cancer statistics and cohort study, the prevalence of distribution of breast cancer subtypes for primary breast cancer in the United States was 68% in HR+/HER2–, 10% in HR+/HER2+, 10% in TNBC, 4% in HR–/HER2+ or 7% in unknown subtype in early breast cancer11,24.