According to the status of the hormone receptors (ER and PR) and HER2 (ERBB2), breast cancer is categorized into four primary subtypes: Lumina-A, Lumina-B, HER2 positive, and triple negative breast cancer (TNBC) (Denkert et al., 2017), each subtype has a matching treatment. The gene discussed is ERBB2; the disease is breast cancer.