BRCA1 and breast cancer: Early-onset BC (EO-BC) and EO-OC are well-known key clinical features of hereditary BC and OC syndrome related to BRCA1 and BRCA2. Women with BRCAm, especially BRCA1 mutation carriers, are at increased risk of EO-BC and EO-OC; the cumulative risk of EO-BC (<40 years old) ranges from 12% to 25%, and that of EO-OC (<50 years old) ranges from 8% to 14% [5,6,7,8,9,10,11].