When activated with other receptors, it initiates multiple signaling pathways leading to epithelial cell growth, proliferation, and survival.3 Overexpression of HER2 results in increased receptor tyrosine kinase activity and upregulation of downstream pathways, including the mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K) pathways.3,4 Through these mechanisms, HER2 amplification drives tumor development and progression. The gene discussed is ERBB2; the disease is neoplasm.