PIK3CA and breast cancer: In the case of breast cancer, genetic linkage analysis and next generation sequencing studies have found that higher penetrance mutations occur mainly in the genes encoding: breast cancer 1 (BRCA1), tumor protein p53 (TP53), phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), retinoblastoma 1 (RB1), phosphatase and tensin homolog (PTEN), GATA binding protein 3 (GATA-3) and mitogen-activated protein kinase kinase kinase 1 (MAP3K1) [5–7].