“HER2 testing is an integral part of diagnosing and making treatment recommendations for cancer, with specific breast and gastric cancer testing guidelines provided by the American Society of Clinical Oncology (ASCO), in collaboration with the College of American Pathologists (CAP). HER2 testing is required for all newly diagnosed patients with breast cancer, along with tissue testing for individuals who develop metastatic disease. For individuals with gastric cancer, HER2 testing of tumor tissue is strongly recommended for individuals with advanced gastroesophageal adenocarcinoma who may be candidates for HER2-targeted therapy. Given well-defined guidelines for the conduct, interpretation, and clinical application of HER2 testing for these populations, we reviewed the current status of testing and barriers for both providers and individuals with or at risk for a cancer diagnosis.”