ERBB2 and breast cancer: In clinical practice, most BC tumors are classified as Luminal A or B, HER-2 positive, or triple negative (TN) based on pathological parameters in immunohistochemistry, such as hormone receptor status, HER-2 status, grade, and proliferation index (Ki-67), that have been well defined (12), although they do not perfectly correspond to the molecular subtypes defined by Perou (13).