ERBB2 and breast cancer: The classification results of any two subtypes of breast cancer include (1) luminal A vs. luminal B, (2) luminal A vs. HER2(+), (3) luminal A vs. TNBC, (4) luminal B vs. HER2(+), (5) luminal B vs. TNBC, and (6) HER2(+) vs. TNBC.