Furthermore, our research not only validated previous findings about some of the co-occurring and mutually exclusive mutations30 but also showed several significant insights: (1) molecular subtypes of breast cancer were validated by the relationship between germline BRCA1/BRCA2/ATM variants and recurrent TP53 and uncommon PIK3CA/GATA3 somatic aberrations; and (2) germline MUTYH variants were found to co-occur with BRCA1 somatic mutations, which may indicate that MUTYH and BRCA1 have a potential synergistic effect on the occurrence and therapeutic efficacy of breast cancer. Here, PIK3CA is linked to breast cancer.