ERBB2 and breast carcinoma: Hormone (estrogen or progesterone) receptor-positive breast cancer and ERBB2 (HER2)-positive breast cancer currently account for 75–80% and 15–20% of breast cancer cases, respectively, with about half of ERBB2-positive cases co-expressing hormone receptors.The remaining 10–15% of breast cancers are defined as triple-negative breast cancers (TNBC), and they are characterized by the lack of ER, PR, and HER2 expression5,6.