Gregory A. Lewin
What is a screening mammogram?
A screening mammogram is an x-ray of the breast used to detect breast
changes in women who have no signs of breast cancer. It usually involves
two x-rays of each breast. Using a mammogram, it is possible to detect a
tumor that cannot be felt.
2. What is a diagnostic mammogram?
A diagnostic mammogram is an x-ray of the breast used to diagnose
unusual breast changes, such as a lump, pain, nipple thickening or
discharge, or a change in breast size or shape. A diagnostic mammogram is
also used to evaluate abnormalities detected on a screening mammogram. It
is a basic medical tool and is appropriate in the workup of breast
changes, regardless of a woman's age.
3. What is the position of the National Cancer Institute
(NCI) on screening mammograms?
The National Cancer Institute recommends that women in their forties or
older get screening mammograms on a regular basis, every 1 to 2 years.
Women who are at increased risk for breast cancer should seek medical
advice about when to begin having mammograms and how often to be screened.
(For example, a doctor may recommend that a woman at increased risk begin
screening before age 40 or change her screening intervals to every year.)
4. What are the factors that place a woman at increased risk
for breast cancer?
Every woman has some risk for developing breast cancer during her
lifetime, and that risk increases as she ages. However, the risk of
developing breast cancer is not the same for all women. These are the
factors known to increase a woman's chance of developing this disease:
- Personal History:
Women who have had breast cancer are more likely to develop a second
- Family History:
The risk of getting breast cancer increases for a woman whose mother,
sister, or daughter has had the disease; or who has two or more close
relatives, such as cousins or aunts, with a history of breast cancer
(especially if diagnosed before age 40). About 5 percent of women with
breast cancer have a hereditary form of this disease.
- Genetic Alterations:
Specific alterations in certain genes, such as those in the breast
cancer genes BRCA1 or BRCA2, make women more susceptible to breast
- Abnormal Biopsy:
Women with certain abnormal breast conditions, such as atypical
hyperplasia or LCIS (lobular carcinoma in situ), are at increased risk.
- Other conditions associated with an increased risk of breast cancer:
- Women age 45 or older who have at least 75 percent dense tissue on
a mammogram are at elevated risk. (This is not only because tumors
in dense breasts are more difficult to "see," but because,
in older women, dense breast tissue itself is related to an
increased chance of developing breast cancer.)
- Women who received chest irradiation for conditions such as
Hodgkin's disease at age 30 or younger are at higher risk for breast
cancer throughout their lives and require regular monitoring for
- A woman who has her first child at age 30 or older has an
increased risk of breast cancer.
- Recent evidence suggests that menopausal women who have long-term
exposure (greater than 10 years) to hormone replacement therapy (HRT)
may have a slightly increased risk of breast cancer.
5. What are the chances that a woman in the United States
might get breast cancer?
Age is the most important factor in the risk for breast cancer. The
older a woman is, the greater her chance of getting breast cancer. No
woman should consider herself too old to need regular screening
mammograms. A woman's chance...
- by age 30... 1 out of 2,525
- by age 40... 1 out of 217
- by age 50... 1 out of 50
- by age 60... 1 out of 24
- by age 70... 1 out of 14
- by age 80... 1 out of 10
Source: NCI's Surveillance, Epidemiology, and
End Results Program & American Cancer Society, 1993.
About 80 percent of breast cancers occur in women over the age of 50;
the number of cases is especially high for women over age 60. Breast
cancer is uncommon in women under age 40.
6. What is the best method of detecting breast cancer as
early as possible?
A high-quality mammogram, with a clinical breast exam (an exam done by
a professional health care provider), is the most effective way to detect
breast cancer early when it is most treatable. Using a mammogram, it is
possible to detect breast cancer that cannot be felt. However, like any
test, mammograms have both benefits and limitations.
When a woman examines her own breasts, it is called breast self-exam (BSE).
Studies so far have not shown that BSE alone reduces the numbers of deaths
from breast cancer. Therefore, it should not be used in place of clinical
breast exam and mammography.
7. What are the benefits of screening mammograms?
- Saved lives:
Several studies have shown that regular screening mammograms can help to
decrease the chance of dying from breast cancer. The benefits of regular
screening are greater for women over age 50. For women in their forties,
there is recent evidence that having mammograms on a regular basis
reduces their chances of dying from breast cancer by about 17 percent.
For women between the ages of 50 and 69, there is strong evidence that
screening with mammography on a regular basis reduces breast cancer
deaths by about 30 percent. Estimates show that if 10,000 women age 40
were screened every year for 10 years, about four lives would be saved.
In comparison, regular screening of 10,000 women age 50 would save about
- More treatment options:
In some cases, finding a breast tumor early may mean that a woman can
choose surgery that saves her breast. Also, a woman whose breast tumor
is detected in its early stages may not have to undergo chemotherapy.
8. What are some of the limitations of screening mammograms?
- Detection does not always mean saving lives:
Even though mammography can detect most tumors that are 5 millimeters in
size, (5 millimeters is about 1/4 inch) and some as small as 1
millimeter, finding a small tumor does not always mean that a woman's
life will be saved. Mammography may not help a woman with a fast-growing
or aggressive cancer that has already spread to other parts of her body
before being detected.
- False Negatives:
False negatives occur when mammograms appear normal even though breast
cancer is actually present. False negatives are more common in younger
women than in older women. The dense breasts of younger women contain
many glands and ligaments, which make breast cancers more difficult to
spot in mammograms. As women age, breast tissues become more fatty and
breast cancers are more easily "seen" by screening mammograms.
Screening mammograms miss up to 25 percent of breast cancers in women in
their forties compared with about 10 percent of cancers for older women.
- False Positives:
False positives occur when mammograms are read as abnormal, but no
cancer is actually present. For women at all ages, between 5 percent and
10 percent of mammograms are abnormal and are followed up with
additional testing (a diagnostic mammogram, fine needle aspirate,
ultrasound, or biopsy). Most abnormalities will turn out not to be
cancer. False positives are more common in younger women than older
women. About 97 percent of women ages 40 to 49 who have abnormal
mammograms turn out not to have cancer, as compared with about 86
percent for women age 50 and older. But all women have to undergo
followup procedures when they have an abnormal mammogram.
Over the past 30 years, improvements in mammography have resulted in an
ability to detect a higher number of small tissue abnormalities called
ductal carcinomas in situ (DCIS), abnormal cells confined to the milk
ducts of the breast. Some of these can eventually go on to become actual
cancers, but many do not. Because it is not possible to predict which
ones will progress to invasive cancer, DCIS is commonly removed
surgically; some are treated with mastectomy, some with breast-sparing
surgery. There is disagreement among experts about the extent of surgery
necessary for DCIS.
Younger women have a higher proportion of DCIS than older women.
Approximately 45 percent of breast cancers detected by screening
mammograms in women ages 40 to 49 are DCIS compared with about 20 to 30
percent of those detected in women age 50 and older.
9. How much does a mammogram cost?
Most screening mammograms cost between $50 and $150. Most states now
have laws requiring health insurance companies to reimburse all or part of
the cost of screening mammograms. Details can be provided by insurance
companies and health care providers.
Some state and local health programs and employers provide mammograms
free or at low cost. Information on low-cost or free mammography screening
programs is available through the NCI's Cancer Information Service at
10. Where can a woman get a high quality mammogram?
Women can get high quality mammograms in breast clinics, radiology
departments of hospitals, mobile vans, private radiology offices, and
Through the Mammography Quality Standards Act, all mammography
facilities are required to display certification by the Food and Drug
Administration (FDA). To be certified, facilities must meet standards for
the equipment they use, the people who work there, and the records they
keep. Women should go to an FDA-certified facility and look for the
certificate and expiration date. Women can ask their doctors or staff at
the mammography facility about FDA-certification before making an
appointment. Information about local FDA-certified mammography facilities
is available through NCI's Cancer Information Service at 1-800-4-CANCER.
11. What technologies are under development for breast
The NCI is supporting the development of several new technologies to
detect breast tumors. This research ranges from technologies under
development in research labs to those that have reached the stage of
testing in humans, known as clinical trials.
Efforts to improve conventional mammography include digital
mammography, where computers assist in the interpretation of the x-rays.
Other studies are aimed at developing teleradiology, sending x-rays
electronically, for long-distance clinical consultations. A non-X-ray
based technology under development is magnetic resonance imaging (MRI).
In addition to imaging technologies, NCI-supported scientists are
exploring methods to detect markers of breast cancer in blood, urine, or
nipple aspirates that may serve as early warning signals for breast
12. What studies is NCI supporting to find better ways to
prevent and treat breast cancer?
NCI is supporting many studies that are looking for improved prevention
and treatment for breast cancer.
- Basic Research:
Many studies are taking place to identify the causes of breast cancer,
including an analysis of the role that alterations in the BRCA1 and
BRCA2 genes play in the development of cancer. Scientists also are
looking at how these genes interact with other genes and with hormonal,
dietary, and environmental factors to determine what influences the
development of breast cancer.
Researchers are looking for ways to prevent breast cancer in women who
are at increased risk. In addition, studies currently under way
involving diet and nutrition could also lead to new prevention
Several studies are aimed at finding treatments for breast cancer that
are more effective and less toxic than current methods.