Editing Breast cancer (section)

=== Genetics ===

Around 10% of those with breast cancer have a family history of the disease or genetic factors that put them at higher risk.{{sfn|Loibl|Poortmans|Morrow|Denkert|2021|loc="Epidemiology and risk factors"}} Women who have had a first-degree relative (mother or sister) diagnosed with breast cancer are at a 30–50% increased risk of being diagnosed with breast cancer themselves.{{sfn|Hayes|Lippman|2022|loc="Inherited germline susceptibility factors"}} In those with zero, one or two affected relatives, the risk of breast cancer before the age of 80 is 7.8%, 13.3%, and 21.1% with a subsequent mortality from the disease of 2.3%, 4.2%, and 7.6% respectively.<ref>{{cite journal | title = Familial breast cancer: collaborative reanalysis of individual data from 52 epidemiological studies including 58,209 women with breast cancer and 101,986 women without the disease | journal = Lancet | volume = 358 | issue = 9291 | pages = 1389–99 | date = October 2001 | pmid = 11705483 | doi = 10.1016/S0140-6736(01)06524-2 | author1 = Collaborative Group on Hormonal Factors in Breast Cancer }}</ref>

Women with certain genetic variants are at higher risk of developing breast cancer. The most well known are variants of the [[BRCA mutation|BRCA genes]] ''BRCA1'' and ''BRCA2''.{{sfn|Hayes|Lippman|2022|loc="Inherited germline susceptibility factors"}} Women with pathogenic variants in either gene have around a 70% chance of developing breast cancer in their lifetime, as well as an approximately 33% chance of developing [[ovarian cancer]].{{sfn|Loibl|Poortmans|Morrow|Denkert|2021|loc="Epidemiology and risk factors"}}{{sfn|Hayes|Lippman|2022|loc="Inherited germline susceptibility factors"}} Pathogenic variants in ''[[PALB2]]'' – a gene whose product directly interacts with that of ''BRCA2'' – also increase breast cancer risk; a woman with such a variant has around a 50% increased risk of developing breast cancer.{{sfn|Loibl|Poortmans|Morrow|Denkert|2021|loc="Epidemiology and risk factors"}} Variants in other [[tumor suppressor]] genes can also increase one's risk of developing breast cancer, namely ''[[p53]]'' (causes [[Li–Fraumeni syndrome]]), ''[[PTEN (gene)|PTEN]]'' (causes [[Cowden syndrome]]), and ''[[PALB1]]''.{{sfn|Hayes|Lippman|2022|loc="Inherited germline susceptibility factors"}}