PIK3CA and breast cancer: Phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), encoding the p110α catalytic subunit of PI3K, as well as phosphatase and tensin homolog (PTEN), which are the suppressors of the PI3K/protein kinase B (Akt) signaling pathway, are frequently mutated in breast cancer [51,52].