Genetically linked breast cancer (up to 4%) are thought to be linked to mutations in the BRCA1 and/or BRCA2 gene(s). However, as noted by Mukhlif above, non-genetically linked breast cancers (sporadic breast cancer) are associated with mutations in a number of genes that encode proteins that participate in the genomic surveillance in cells. Some of these genes are listed by Mukhlif. Notably, mutations in the genes that immortalize breast cells and bypass the p53 and Rb/E2F-mediated cell cycle checkpoint regulation contribute to the development of breast cancer. The list of these genes is likely to be long.