Not only a wealth of examinations including breast ultrasound, mammography and MRI have been conducted, which can diagnose breast cancer patients in early stage (3), but breast cancer has evolved from classical markers providing basic tissue diagnosis, such as ER and HER2, to a series of comprehensive biomarkers including BRCA1/2, PIK3CA, FOXA1 and NAT1 based on protein expression and molecular prognosis (4–6). Here, PIK3CA is linked to breast cancer.