What is the role of family history in the etiology of breast cancer?

Updated: Dec 27, 2019
  • Author: Pavani Chalasani, MD, MPH; Chief Editor: John V Kiluk, MD, FACS  more...
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Answer

A positive family history of breast cancer is the most widely recognized risk factor for breast cancer. The lifetime risk is up to 4 times higher if a mother and sister are affected, and it is about 5 times greater in women who have two or more first-degree relatives with breast cancer. The risk is also greater among women with breast cancer in a single first-degree relative, particularly if the relative was diagnosed at an early age (≤50 years).

Despite a history indicating increased risk, many of these families have normal results on genetic testing. However, identification of additional genetic variants associated with increased risk may prove valuable. Michailidou et al conducted a controlled genome-wide association study (GWAS) of breast cancer that included 122,977 cases of European ancestry and 14,068 cases of East Asian ancestry, and identified 65 new loci associated with overall breast cancer risk. [8] A GWAS by Milne et al identified 10 variants at 9 new loci that are associated with risk of estrogen receptor–negative breast cancer. [9]

A family history of ovarian cancer in a first-degree relative, especially if the disease occurred at an early age (< 50 years), has been associated with a doubling of breast cancer risk. This often reflects inheritance of a pathogenic mutation in the BRCA1 or BRCA2 gene.


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