PIK3CA and breast cancer: In breast cancer, approximately 32–37% of all patients with advanced disease harbor a PIK3CA mutation, with the most frequent alterations being p.H1047R (23.1%), p.E545K (23.1%), p.E542K (16.3%), p.H1047L (3.2%) and p.N345K (3.1%, among all PIK3CA mutations) [8, 9].