ERBB2 and neoplasm: HER2 is a transmembrane RTK which lacks specific ligands and which transmits cell proliferation signals by forming heterodimers with other HER family members, leading to phosphorylation of tyrosine residues and triggering downstream signaling cascades that regulate cancer cell survival, proliferation, apoptosis, differentiation, motility, adhesion, invasion, and migration, and tumor angiogenesis (Yarden and Sliwkowski 2001; Guo et al. 2023).