ERBB2 and breast carcinoma: To date, breast cancer has been found to have at least four distinct molecular subtypes, which can be determined by gene expression profiling: Luminal A (Hormone Receptor (HR)-positive and Human Epidermal Growth Factor receptor 2 (HER2)-negative), Luminal B (HR+/HER2+), Triple-Negative Breast Cancer (TNBC), and HER2+ [5].