Although HER2-positive breast cancer is known to be aggressive, and patients with HER2-positive breast cancer had a poorer prognosis, anti-HER2 therapy, such as trastuzumab, pertuzumab, and TDM-1, which are recombinant antibodies that target HER2-positive cancer cells, have dramatically improved survival of patients with this subtype. Here, ERBB2 is linked to cancer.