Medullary breast cancer and germline BRCA1 mutations: a possible criterion for genetic testing

Medullary breast cancer is a rare subtype of invasive breast cancer, representing from 0.2% to 6% of all breast carcinomas, with a higher proportion among women with triple-negative breast cancer and among those with a BRCA1 mutation. This review article aims to investigate the frequency of medullary breast cancer among all breast cancers and to assess its association with BRCA1 mutations. We surveyed studies involving patients diagnosed with breast cancer that report both the histology of the breast cancer as well as the presence of BRCA1 mutations. Among women with medullary breast cancer, the proportion of cases that carry a BRCA1 mutation ranges from 3% up to 35.3%, depending on the study. Among BRCA1-mutated breast cancers, the proportion that are medullary ranges from 8 to 20%. Given the notable association between medullary breast cancer and BRCA1 mutations, we propose to consider medullary breast cancer as a criterion for genetic testing in order to improve the identification of a larger number of carriers, thereby enhancing screening and prevention strategies.