PIK3CA and breast cancer: Several other genes are also involved in signaling and DNA repair defect in breast cancer such as fanconi anemia (FA) genes (FANCD2, FANCA, FANCC), mismatch repair endonuclease PMS2, mismatch repair genes (MutL homolog 1 (MLH1)), ataxia-telangiectasia, mutated (ATM) and Phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) genes [40,41].