ERBB2 and breast carcinoma: Luminal-type breast cancer is the most common type and is divided into two subtypes, luminal A and luminal B. This subtype is defined as having a low Ki-67 in comparison to hormonal receptor (HR)-negative breast cancer subtypes, which are HER2+ and basal-like, that have higher Ki-67 indexes and are, therefore, higher-grade tumors [4].