PTEN and breast cancer: The main mutations observed in BC within this pathway are mutated PTEN or loss of PTEN heterozygosity, and mutation of phosphatidylinositol-4,5-biphosphate 3-kinase catalytic subunit alpha (PIK3CA), mTOR, tuberous sclerosis 1 (TSC1), and AKT genes (Pathway A, Figure 1) [14,15].