Estrogen Receptor Status in <b> <i>BRCA1</i> </b>- and <b> <i>BRCA2</i> </b>-Related Breast Cancer

The strong relationship between the presence of a BRCA1 mutation and the ER-negative status of the breast cancers is neither a consequence of the young age at onset nor the high grade but is an intrinsic property of BRCA1-related cancers. The ER-negative status of these cancers may reflect the cell of origin of BRCA1-related cancers.