Targeted therapies for breast cancer have traditionally only been based on hormone receptors (HR) and HER2 status: for patients with estrogen- and progesterone-positive (ER/PR +) cancer, endocrine therapy (e.g., tamoxifen) is used, whereas for patients with HER2 + cancer, antiHER2-targeted therapy is used [7]. The gene discussed is ERBB2; the disease is cancer.