Aberrant gene expression plays an important role in tumorigenesis, progression and metastasis of breast cancer and it is considered to be the consequence of not only genetic defects (such as TP53, PIK3CA mutation, BRCA1/BRCA2 inactivation, Cyclin D1 amplification 2) but also epigenetic modifications 3. This evidence concerns the gene PIK3CA and breast carcinoma.