Recent progress in immunohistochemistry (IHC) has helped clinicians to identify the presence of specific biomarkers and to categorize patients in pathology.21, 22 Detection of human epidermal growth factor receptor 2 (HER2)23 in breast cancer and PD-L124 in lung cancer based on IHC aided the prescription of suitable drugs for the patients. The gene discussed is ERBB2; the disease is breast carcinoma.