ERBB2 and breast cancer: The PI3K pathway is a prototypic survival pathway and is the most frequently dysregulated pathway in BC[15], through a variety of genetic disruptions such as deletion of the tumour suppressor PTEN, oncogenic mutations in phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha mutation (PIK3CA), and/or HER2 amplification[16].