ERBB2 and breast neoplasm: Clinically, hormone receptor-positive (HR + )/luminal A breast tumors are most differentiated with better survival outcomes, whereas the luminal B, HER2-enriched (HER2-E) and triple-negative (TNBC) subtypes show aberrant/blocked differentiation, enrichment with stem-like cells, higher proliferation and metastatic rates, and the worst survival outcomes [10, 11].