The human epidermal growth factor receptor 2 gene (ErbB2/HER2, hereafter called ErbB2), encodes a 185-kDa transmembrane protein that belongs to the epidermal growth factor receptor family.3, 4 Through its downstream signaling pathways, such as the mitogen-activated protein kinase (MAPK) pathway, ErbB2 regulates several important cell functions in cancer development and progression, such as growth, differentiation, and apoptosis.5 The ErbB2 gene is amplified or overexpressed in approximately 25% of human breast carcinomas and plays a role in many other human malignancies.6, 7. The gene discussed is ERBB2; the disease is breast carcinoma.