The College of American Pathologists/American Society for Clinical Pathology/American Society of Clinical Oncology guidelines [4], Japanese Guidelines for HER2 Testing in Breast Cancer/Gastric Cancer [5], and the Japanese Classification of Gastric Carcinoma [29] have presented the specimen handling in detail, and for laboratories that conduct HER2 testing, these guidelines strongly recommend adopting the same tests in the program to improve the overall quality of the laboratories and to establish an appropriate monitoring system to improve quality. The gene discussed is ERBB2; the disease is breast cancer.