BRCA1 and breast cancer: There is evidence, however, that ER-positive tumours arising in BRCA1/2m carriers have different morphologic features than ER-positive tumours arising in non-carriers, with those in carriers more frequently exhibiting a higher histologic grade, higher oncotype recurrence score, and more often classified as luminal B by gene expression profiling.16,107–109 Furthermore, the percentage of ER-positive BC increases with increasing patient age in BRCA1m carriers, but decreases with increasing age in BRCA2m carriers.16,107