ESR1 and ductal breast carcinoma in situ: However, while most BRCA1-associated tumors were triple negative, still a substantial number of BRCA1-associated DCIS had expression of ER (20.8 %) or PR (20.8 %), which supports previous studies that have demonstrated the benefit of anti-estrogen therapy and oophorectomy in BRCA1 patients [28, 29, 32].