RESUMEN
<p><b>OBJECTIVE</b>The phosphatidylinositol-3-kinase (PI3K)-AKT signaling pathway is considered to play an important role in tumorigenesis. Frequent somatic mutations in the PI3K subunit p110a (PIK3CA) occur in a variety of cancer types. The purpose of this study was to determine the relationship between PIK3CA mutation in breast cancer and pathological features and outcome of patients.</p><p><b>METHODS</b>The PIK3CA mutations in exons 7, 9, 20 were screened in 250 primary breast cancers using PCR and fluorescent (F)-SSCP, and the results were analyzed according to their cliniopathological data.</p><p><b>RESULTS</b>The frequency of PIK3CA mutations among the 250 cases was 35.2% (88/250), point mutations in exon 7 were found in 8 (3.2%) cases,40 (16.0%) cases in exon 9 and 47 (18.8%) cases in exon 20. No significant correlation between PIK3CA mutation and age, histological type, differentiation, and lymph node metastasis was observed. Mutations were associated with larger tumor size (P = 0.004) and positive estrogen receptor status (P = 0.008). Patients with PIK3CA mutations showed a significantly worse survival (P = 0.004), particularly in those with positive estrogen receptor expression or non-amplified HER-2 (both P = 0.002).</p><p><b>CONCLUSIONS</b>PIK3CA mutations may play an important role in the carcinogenesis and development of breast cancer. The association with large tumor size, ER+ and poor survival indicates that PIK3CA mutation could be an independent factor for tumor malignant phenotype and prognosis.</p>