HER2 receptor activation, either by homodimerization when there is an abundance of HER2 receptors or heterodimerization after stimulation of certain dimerization partner receptors with a pertinent ligand, leads to subsequent activation of PI3K/Akt and Ras/ERK/MAPK signalling pathways responsible for the naturally high proliferation and aggressiveness of these tumours. This evidence concerns the gene AKT1 and neoplasm.