In this study, we found high prevalence of mutations of KRAS, PIK3CA, MAP3K1, MAP2K4, PTEN, TP53, CDH1, GATA3, KMT2C, ARID1A, RunX1, and ESR1 genes occurring in primary tumor specimens of BC patients, including triple-negative and luminal A patients. The gene discussed is ARID1A; the disease is neoplasm.