ERBB2 and breast ductal adenocarcinoma: Clinically, ductal carcinoma is evaluated according to the expression profile of the estrogen (ER), progesterone (PR), and epidermal growth factor type 2 receptor (HER2), and it is subclassified into hormone-positive receptors (Luminal A, Luminal B), and HER2-positive and triple negative for hormone receptors (basal-like) [18].