ERBB2 and breast neoplasm: Breast cancers both expressing ER and PR represent approximately 85% of all breast cancers and are further divided into two subtypes: luminal A, which includes ER+ and/or PR+ and HER2- breast cancer, and is characterised by the low expression of Ki-67 proliferation marker, and luminal B, which includes ER+ and/or PR+, HER2+ (or HER2-) breast tumours, showing high Ki-67 expression and worse prognosis than Luminal A. Both HER2+ and TNBCs account for about 15% of breast cancers [1].