HER2: human epidermal growth factor receptor 2; HR: hormone receptor; BMI: body mass index; IDC: invasive ductal carcinoma; ILC: invasive lobular carcinoma; SBR: Scarff-Bloom-Richardson grade; Ki-67: proliferation index; BCS: breast-conserving surgery; BRS: mastectomy (breast radical surgery); RT: radiotherapy; T: tumor size (TNM classification); N: nodal status (TNM classification). This evidence concerns the gene ERBB2 and invasive ductal breast carcinoma.