In BC, the most frequent PIK3CA mutations lead to protein residue changes at the following positions of exon mutations: E542K (76–78), E545K (77, 78) in exon 9 and H1047R (77, 78) in exon 20, comprising approximately 78% of all PIK3CA mutations observed in breast tumors (79). This evidence concerns the gene PIK3CA and breast cancer.