ERBB3 and neoplasm: Activation of HER3-containing heterodimers leads to HER3 phosphorylation and subsequent activation of signaling pathways, including phosphatidylinositol 3-kinase (PI3K)/Akt and RAF/MEK/extracellular signal-regulated protein kinase (ERK) pathways, that drive tumor cell proliferation and promote survival [2,4].