Ghasem Azizi Tabesh - Medical Genetics Department, Medical School, Tehran University of Medical Sciences, Tehran, Iran.
Pantea Izadi - Medical Genetics Department, Medical School, Tehran University of Medical Sciences, Tehran, Iran.
Javad Tavakkoly Bazzaz - Medical Genetics Department, Medical School, Tehran University of Medical Sciences, Tehran, Iran

Introduction & Aim: Genetic alterations in the components of PI3K signaling pathway, as well as activating mutations in the p110α catalytic subunit of PI3K (PIK3CA), have been detected in a wide range of human cancers including colon, ovarian, lung, brain, liver, endometrial, and breast cancer. PIK3CA gene currently appears to be the most frequently mutated oncogene in breast tumor. And also the vast majority of PIK3CA mutations are located in exons 9 and 20. Material and methods: In this study, we have investigated the distribution and frequency of PIK3CA mutations in the exons 9 and 20 in 80 breast tumors separately by PCR and DNA sequencing methods and subsequently assessed the association of PIK3CA mutations with clinicopathplogical features. Results: PIK3CA mutations were determined in 36 (45%) of the tumors; these mutations were found more in progesterone receptor positive and Her2 negative tumors Conclusion: PIK3CA mutations status did not significantly associate with age at diagnosis, tumor size,lymph node involvement, stage of tumor, and ER status whereas PIK3CA mutations often tended to be present in PR positive (p: 0.06), and Her2 negative tumors(P: 0.09), and more frequent in tumors with low grades(P: 0.01). Prognosis results by NPI method show that PIK3CA mutations associate more with good prognosis in comparison with wild type gene.