The silencing of the BRCA1 gene by promoter DNA hypermethylation occurs in breast cancer (13%), but depending on cancer subtypes, BRCA1 promoter hypermethylation is present in 55% of sporadic mucinous breast carcinomas and in 67% of medullary breast carcinomas [91,93,94]. The gene discussed is BRCA1; the disease is breast carcinoma.