In light of the critical role of the PTEN/PI3K/AKT pathway in maintaining proper cellular function, it is possible that some candidate functional SNPs of genes which located in the 5′-untranslated regions (5′UTR) and 3′ UTRs of this pathway may have an effect on susceptibility and response to chemotherapy and prognosis of breast cancer. The gene discussed is PIK3CA; the disease is breast cancer.