Expression of these receptors influences treatment decisions as the presence of the estrogen receptor (ER), expressed in ~80% of breast tumors (18), determines a tumor's response to endocrine therapy while expression of HER2 (19) means that the cancer can be treated with monoclonal antibodies that specifically target this receptor, such as trastuzumab (herceptin) (20, 21). Here, ERBB2 is linked to breast neoplasm.