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:
Personal
history of breast cancer. Women
who have had breast cancer face an increased risk of getting breast cancer
again.
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.
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.
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:
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.
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.
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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