ERBB2 and breast cancer: Activation of Her2 through homodimerization or heterodimerization upon ligand binding triggers a cascade of its downstream events, eventually leading to activation of multiple signaling pathways including Ras/Raf/mitogen-activated protein kinase (MAPK) and phosphatidylinositol-3-kinase (PI3K)/Akt pathways, which critically regulate rapid growth, survival, and migration of tumor cells and confer resistance to the anticancer agents in breast cancer [1, 2].