PIK3CA and breast cancer: Eighty-one genes were mutated in at least 5 % of samples, among them 13 from the top 20 list of most frequently mutated breast cancer genes in the COSMIC database (cancer.sanger.ac.uk) [23]: (PIK3CA, AKT1, GATA3, TP53, MLL2, MAP2K4, NF1, ARID1A, CDH1, MED12, PTEN, BRCA1, APC).