Using these biomarkers, BC is classified into three major molecular subtypes: hormone sensitive (ER+/PR+ or ER+/PR−, HER2−); HER2 amplified (ER−/PR− or ER+/PR−, HER2+); and triple negative (TNBC) (ER−/PR−/HER2−) [3]. The gene discussed is ERBB2; the disease is breast cancer.