The new stratification of breast cancers from HER2-negative to HER2-low or HER2-zero subclasses (noting that HR−/HER2-zero = triple negative) in our cohort has shown that HER2-low subclasses comprise over 50% of HR+/HER2-negative and ~40% of previousy classified triple negative breast cancers for both advanced and early breast cancers. Here, ERBB2 is linked to breast cancer.