Abstract: Objective To find the correlation between phosphatidylinositol kinase-3 catalytic subunit A gene (PIK3CA) mutation and pathological features as well as clinical prognosis of breast cancer. Methods The pathological data of 181 patients diagnosed with invasive breast cancer from January 2018 to January 2020 were collected. The estrogen receptor(ER), progestogen receptor(PR), human epidermal growth factor receptor-2(HER2), Ki67 were examined by immuno-histochemistry(IHC).Mutation of exon 9 and exon 20 of PIK3CA were examined by quantitative real-time PCR(qPCR). Results Among 181 cases of invasive breast cancer, 70 cases had PIK3CA mutation with 31 cases (44.28%) showed exon 9 mutations and 39 cases (55.71%) showed exon 20 mutations. The difference between PIK3CA mutation and their distribution in molecular typing of breast cancer was statistically significant(P＜0.05). The expression of PIK3CA mutation in breast cancer with different Ki67 expression was significantly different(P＜0.05). There were 34 cases (48.57%) showed PIK3CA mutations in the HR+/HER2 group and 36 cases (51.43%) of non HR+/HER2 group mutations. There was a statistically significant difference in the distribution of PIK3CA mutations between 2 groups(P＜0.05). The death rate of PIK3CA mutation cases was higher than that of PIK3CA wild type cases (P＜0.05). Conclusions PIK3CA mutation is associated with molecular typing, Ki67 increment index and prognosis of breast cancer. Detection of PIK3CA mutation provides potential support to the development of precise treatment of breast cancer patients.

Key words: breast cancer, phosphatidylinositol kinase-3-catalytic subunit(PIK3CA), estrogen receptor, progestogen receptor, human epidermal growth factor receptor 2