In breast cancer, somatic mutations of PIK3CA oncogene are common. We investigated the mutational status of exons 9 and 20 of the PIK3CA gene by polymerase chain reaction and direct sequencing in 80 breast tumors, and observed that 45% of these contained PIK3CA mutations in the mentioned exons. These mutations were found more in progesterone receptor positive and Her2- tumors, but this association did not reach a statistically significant level. Also, we observed a significant association between PIK3CA mutations and low-grade tumors. In our study, PIK3CA mutations were related to good and moderate prognosis in breast cancer patients.
Keywords: Breast cancer; PIK3CA; somatic mutation.