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Risk Factors for
Breast Cancer
The risk of breast cancer increases gradually as a woman gets older. This
disease is uncommon in women under the age of 35. All women age 40 and older
are at risk for breast cancer. However, most breast cancers occur in women
over the age of 50, and the risk is especially high for women over age 60.
Research has shown that the following conditions place a woman at
increased risk for breast cancer:
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Personal history of breast cancer. Women who have had breast
cancer face an increased risk of getting breast cancer again.
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Genetic alterations. Changes in certain genes (BRCA1, BRCA2,
and others) make women more susceptible to breast cancer. In families in
which many women have had the disease, gene testing can show whether a
woman has specific genetic changes known to increase the susceptibility
to breast cancer. Doctors may suggest ways to try to delay or prevent
breast cancer, or improve the detection of breast cancer in women who
have the genetic alterations. For more information about gene testing,
read the Causes and Prevention section
under The Promise of Cancer Research.
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Family history. A woman's risk for developing breast cancer
increases if her mother, sister, daughter, or two or more other close
relatives, such as cousins, have a history of breast cancer, especially
at a young age.
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Certain breast changes. Having a diagnosis of atypical
hyperplasia or lobular
carcinoma in situ (LCIS) or having had two or more breast biopsies
for other benign conditions may increase a woman's risk for developing
cancer.
Other factors associated with an increased risk for breast cancer
include:
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Breast density. Women age 45 and older whose mammograms
show at least 75 percent dense tissue are at increased risk. Dense
breasts contain many glands and ligaments, which makes breast tumors
difficult to "see," and the dense tissue itself is associated
with an increased chance of developing breast cancer.
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Radiation therapy.
Women whose breasts were exposed to radiation during their childhood,
especially those who were treated with radiation for Hodgkin's disease,
are at an increased risk for developing breast cancer throughout their
lives. Studies show that the younger a woman was when she received her
treatment, the higher her risk for developing breast cancer later in
life.
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Late childbearing. Women who had their first child after the
age of 30 have a greater chance of developing breast cancer than women
who had their children at a younger age.
Also at a somewhat increased risk for developing breast cancer are women
who started menstruating at an early age (before age 12), experienced menopause
late (after age 55), never had children, or took hormone replacement therapy
or birth control pills for long periods of time. Each of these factors
increases the amount of time a woman's body is exposed to estrogen.
The longer this exposure, the more likely she is to develop breast cancer.
In most cases, doctors cannot explain why a woman develops breast cancer.
Studies show that most women who develop breast cancer have none of the risk
factors listed above, other than the risk that comes with growing
older. Also, most women with known risk factors do not get breast cancer.
Scientists are conducting research into the causes of breast cancer to learn
more about risk factors and ways of preventing this disease.
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