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Breast Cancer 

Breast Cancer
Chapter:
Breast Cancer
Author(s):

Susan Love

and Dixie J. Mills

DOI:
10.1093/med/9780195378818.003.0022
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date: 18 November 2019

Breast cancer risk appears to be correlated with high levels of endogenous estrogen at certain lifetime periods, including in utero, puberty, and menopause. Increasing age is a risk factor in the Western world as is a maternal or paternal family history. Other risk factors include childhood or adolescent exposure to ionizing radiation, exogenous estrogens, and possibly chemicals and viruses. Table 22.1 illustrates the risk factors that have been identified in numerous epidemiological studies. However, most women who develop breast cancer have few if any of these known risk factors, while some women who have all of them may never develop the disease. Mammographic density is a newly identified risk factor that implicates the role of the breast stroma, which accounts for much of the density reading. Two large tumor suppressor genes, BRCA1 and 2, located on chromosomes 17 and 13, account for approximately 5% of all breast cancers. Women who carry one of these mutations have a lifetime breast cancer risk of 40%–80%, depending on mutation, penetrance, and other host factors. No recommendations exist at this time for population screening for these mutations. Women interested in testing should be counseled and evaluated at a high risk or genetic counseling center.

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