Taking into account the IHC expression of these biomarkers, the classification adopted in the thirteenth St Gallen International Breast Cancer Conference in 2013 [4] divides BC into five molecular subtypes: Luminal A, Luminal B/HER2-negative, Luminal B/HER2-positive, HER2-positive and triple-negative BC (TNBC). The gene discussed is ERBB2; the disease is breast cancer.