ERBB2 and breast carcinoma: Based on molecular biomarkers, breast cancer can be classified into at least four different subtypes, with different treatments and prognoses: HR-negative and HER2-enriched, HR-positive and HER2-negative luminal A, HR-positive and HER2-positive luminal B and triple negative/basal-like, which is a subtype that is negative for both HR and HER2.