ESR1 and breast cancer: When pathologic features and biomarkers expression of all BRCA1-associated cancers (ER+ and ER- combined) were analyzed according to status of loss of wt BRCA1 allele, in univariate analysis, breast cancers with loss of wt BRCA1 were more likely to be of pure invasive ductal type (P = 0.043), to be histologic grade 3 (P = 0.001), and to have a higher mitotic rate (P < 0.001) (Table 1).