PIK3CA and breast cancer: The phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) represents one of the signaling pathways which plays crucial role in cell proliferation, growth and other cellular processes in several cancer types, including BC and more prominently the hormone receptor positive (HR +)/human epidermal growth factor receptor-2 negative (HER2-) subtype [1].