In 2018, the American Society of Clinical Oncology (ASCO) and the College of American Pathologists (CAP) clinical practice guideline proposed that patients whose immunohistochemistry (IHC) results show 0/1+ or IHC 2+ with negative in situ hybridization (ISH) should be diagnosed as having HER2-negative breast cancer, and those with IHC 3+ or IHC 2+ and ISH positive results should be diagnosed as having HER2-positive breast cancer (8). The gene discussed is ERBB2; the disease is breast carcinoma.