ESR1 and cancer: BRCA1 promoter methylation analysis was performed by methylation-specific PCR on 28 cases for which remaining tumor DNA was available, including 6 of the 8 ER+ and 3 of the 4 ER- cancers which did not demonstrate loss of wt BRCA1. Methylation was identified in a single tumor sample, an ER+ low-grade (tubular) carcinoma without genomic loss of wt BRCA1.