A clonal evolution of BRCA1-methylated ectodermal- and mesodermal-derived cancer cells from a common precursor is corroborated by the finding of BRCA1 epimutations across normal tissues derived from all three germ layers as well as an allele-specific concordance of methylation in breast tumor, normal breast tissue, and WBC [31, 52]. The gene discussed is BRCA1; the disease is cancer.