When compared to HR+HER2-low breast cancer, HR+HER2-positive breast cancer had 5 differentially mutated genes (TP53, CDK12, GATA3, KRAS and PIK3CA) and HR+HER2-zero patients only had 3 ones (SETD2, ESR1 and ARID1A). This evidence concerns the gene ARID1A and breast cancer.