BRCA1 and cancer: At the same time a study based on blood derived from 30 breast cancer cases with BRCA1-like phenotype that also used BeadChip microarray, found elevated methylation levels in seven cancer cases with BRCA1-like phenotype, at the CpG sites within BRCA1 promoter that are most studied for constitutional methylation changes but reported methylation differences were less than 10%10.