- What is a mammogram?
A mammogram is an x-ray of the breast.
Mammograms can be used to check for breast cancer in women who have no signs
or symptoms of the disease. This type of mammogram is called a screening
mammogram.
Screening mammograms usually involve two x-rays of each breast. They make
it possible to detect tumors
that cannot be felt. Screening mammograms can also find microcalcifications
(tiny deposits of calcium)
that sometimes indicate the presence of breast cancer.
Mammograms can also be used to check for breast cancer after a lump or other
sign or symptom of breast cancer has been found. This type of mammogram is
called a diagnostic
mammogram. Signs of breast cancer may include pain, skin thickening, nipple
discharge, or a change in breast size or shape. A diagnostic mammogram
also may be used to evaluate changes found during a screening mammogram, or
to view breast tissue
when it is difficult to obtain a screening mammogram because of special circumstances,
such as the presence of breast
implants (see Question 14).
- How are screening and diagnostic
mammograms different?
Diagnostic mammograms take longer than screening mammograms because they
involve more x-rays in order to obtain views of the breast from several angles.
The technician
may magnify a suspicious area to produce a detailed picture that can help
the doctor make an accurate diagnosis.
- When does the National
Cancer Institute (NCI) recommend that women have screening mammograms?
- Women age 40 and older should have mammograms every 1 to 2 years.
- Women who are at higher than average risk of breast cancer should talk
with their health care providers about whether to have mammograms before
age 40 and how often to have them.
- What are the factors that place a woman at
increased risk of breast cancer?
The risk of breast cancer increases gradually as a woman gets older. However,
the risk of developing breast cancer is not the same for all women. Research
has shown that the following factors increase a woman’s chance
of developing this disease:
- Personal
history of breast cancer—Women who have had breast cancer
are more likely to develop a second breast cancer.
- Family
history—A woman’s chance of developing breast cancer
increases if her mother, sister, and/or daughter have been diagnosed with
the disease, especially if they were diagnosed before age 50. Having a close
male blood
relative with breast cancer also increases a woman's risk of developing
the disease.
- Certain breast changes found on biopsy—Looking
at breast tissue under a microscope
allows doctors to determine whether cancer
or another type of breast change is present. Most breast changes are not
cancer, but some may increase the risk of developing breast cancer. Changes
associated with an increased risk of breast cancer include atypical
hyperplasia (a noncancerous condition in which cells
have abnormal
features and are increased in number), lobular
carcinoma in
situ (LCIS) (abnormal cells are found in the lobules
of the breast), and ductal
carcinoma in situ (DCIS) (abnormal cells are found in the lining
of breast ducts).
Because some cases of DCIS will eventually develop into invasive
breast cancer, this type of change is actively treated (see Question
10). Women with atypical hyperplasia and LCIS are usually monitored
carefully and not actively treated. In addition, women who have had two
or more breast biopsies for other noncancerous conditions also have an increased
risk of developing breast cancer. This increased risk is due to the conditions
that led to the biopsies and not to the biopsy procedure itself.
- Genetic
alterations (changes)—Changes in certain genes
(for example, BRCA1,
BRCA2,
and others) increase the risk of breast cancer. These changes are rare;
they are estimated to account for no more than 10 percent of all breast
cancers.
- Reproductive
and menstrual
history—Women who began having menstrual periods before age
12 or went through menopause
after age 55 are at increased risk of developing breast cancer. Women who
have their first child after age 30 or who never have a child are also at
increased risk of developing breast cancer.
- Long-term use of menopausal
hormone therapy—Women who use combination estrogen-progestin
menopausal hormone therapy for more than 5 years have an increased chance
of developing breast cancer.
- Breast
density —Breast density refers to the relative amounts
of different tissue in the breast as seen on a mammogram. Dense breasts
have more glandular
(milk-producing) and connective
tissue than fatty tissue. Low-density breasts have a greater proportion
of fatty tissue. Younger women usually have denser breasts than older women.
As a woman ages, the amount of glandular tissue normally decreases and the
amount of fatty tissue increases. Because breast cancers tend to develop
in the dense tissue of the breast, older women whose mammograms show more
dense tissue have a higher risk of developing breast cancer. Abnormalities
in dense breasts can be more difficult to detect on a mammogram.
- Radiation
therapy—Women who had radiation therapy to the chest
(including the breasts) before age 30 have an increased risk of developing
breast cancer throughout their lives. This includes women treated for Hodgkin
lymphoma. Studies show that the younger a woman was when she received
her treatment, the higher her risk of developing breast cancer later in
life.
- DES (diethylstilbestrol)—The
drug
DES was given to some pregnant women in the United States between 1940 and
1971. (It is no longer given to pregnant women.) Women who took DES during
pregnancy may have a slightly increased risk of breast cancer. The possible
effects on their daughters and granddaughters are under study.
- Body weight—Studies have found that the chance
of getting breast cancer after menopause is higher in women who are overweight
or obese.
- Physical activity level—Women who are physically
inactive throughout life may have an increased risk of breast cancer. Being
active may help reduce risk by preventing weight gain and obesity.
- Alcohol—Studies
indicate that the more alcohol a woman drinks, the greater her risk of breast
cancer.
- What are the chances that a woman in the
United States might develop breast cancer?
Age is the most important risk
factor for breast cancer. The older a woman is, the greater her chance
of developing breast cancer. Most 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 relatively uncommon in women under age 40. The NCI fact sheet Probability
of Breast Cancer in American Women provides more information about lifetime
risk. This fact sheet is available at http://www.cancer.gov/cancertopics/factsheet/Detection/probability-breast-cancer
on the Internet.
- What is the best method of detecting breast
cancer as early as possible?
Getting a high-quality screening mammogram and having a clinical
breast exam (an exam done by a health care provider) on a regular basis
are the most effective ways to detect breast cancer early. As with any screening
test, screening mammograms have both benefits and limitations. For example,
some cancers cannot be detected by a screening mammogram but may be found
by a clinical
breast exam.
Checking one’s own breasts for lumps or other unusual changes is called
a breast
self-exam, or BSE. Breast self-exams cannot replace regular screening
mammograms or clinical breast exams. In clinical
trials (research studies), breast self-exams alone have not been found
to help reduce the number of deaths from breast cancer.
If a woman chooses to do breast self-exams, it is important to remember that
breast changes can occur because of pregnancy, aging, menopause, during menstrual
cycles, or taking birth control pills or other hormones.
It is normal for breasts to feel a little lumpy and uneven. Also, it is common
for breasts to be swollen and tender right before or during a menstrual period.
If a woman notices any unusual changes in her breasts, she should contact
her health care provider.
- What are the benefits of screening mammograms?
Several large studies conducted around the world show that breast cancer
screening with mammograms reduces the number of deaths from breast cancer
for women ages 40 to 69, especially for those over age 50. Studies conducted
to date have not shown a benefit from regular screening mammograms, or from
a baseline
screening mammogram (a mammogram used for comparison), in women under age
40.
- What are some of the limitations or harms
of screening mammograms?
- Finding cancer does not always mean saving lives—Even
though mammograms can detect tumors that cannot be felt, finding a small
tumor does not always mean that a woman’s life will be saved. Screening
mammograms 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 present. Overall, screening mammograms
miss up to 20 percent of the breast cancers that are present at the time
of screening. False negatives occur more often in younger women than in
older women because the dense breasts of younger women make breast cancers
more difficult to detect in mammograms. As women age, their breasts usually
become more fatty (therefore, less dense), and breast cancers become easier
to detect with screening mammograms.
- False positives—False positives occur when radiologists
decide mammograms are abnormal, but no cancer is actually present. All abnormal
mammograms should be followed up with additional testing (a diagnostic mammogram,
ultrasound,
and/or biopsy) to determine if cancer is present. False positives are more
common in younger women, women who have had previous breast biopsies, women
with a family history of breast cancer, and women who are taking estrogen
(for example, hormone
replacement therapy).
- Radiation
exposure—Mammograms (as well as dental x-rays and other routine
x-rays) use very small doses
of radiation. The risk of any harm is very slight, but repeated x-rays could
cause problems. The benefits nearly always outweigh the risk. Women should
talk with their health care provider about the need for each x-ray. They
should also ask about shielding to protect parts of the body that are not
in the picture. In addition, they should always let their health care provider
and the technician know if there is any possibility that they are pregnant.
- What is the Breast Imaging
Reporting and Database System (BI-RADS®)?
The American College of Radiology (ACR) has established a uniform way for
radiologists to describe mammogram findings. The system, called BI-RADS, includes
seven standardized categories, or levels. Each BI-RADS category has a follow-up
plan associated with it to help radiologists and other physicians
appropriately manage a patient’s care.
| Breast Imaging Reporting and Database
System (BI-RADS) |
| Category |
Assessment |
Follow-up |
| 0 |
Need additional imaging evaluation |
Additional imaging needed before a category
can be assigned |
| 1 |
Negative |
Continue annual screening mammograms (for
women over age 40) |
| 2 |
Benign
(noncancerous) finding |
Continue annual screening mammograms (for
women over age 40) |
| 3 |
Probably benign |
Receive a 6-month follow-up mammogram
|
| 4 |
Suspicious abnormality |
May require biopsy |
| 5 |
Highly suggestive of malignancy
(cancer) |
Requires biopsy |
| 6 |
Known biopsy-proven malignancy (cancer)
|
Biopsy confirms presence of cancer before
treatment begins |
Additional information about BI-RADS is available on the ACR Web site at
http://www.acr.org or by calling the ACR
at 1–800–ACR–LINE (1–800–227–5463).
- What happens if a mammogram leads to the
detection of ductal carcinoma in situ (DCIS)?
Over the past 30 years, improvements in mammography have made it possible
to detect a larger number of tissue abnormalities, including DCIS. DCIS is
a condition in which abnormal cells are confined to the milk ducts of the
breast. The cells have not invaded the surrounding breast tissue. DCIS usually
does not cause a lump, so it cannot be detected during a clinical breast exam
or BSE. However, mammography is able to detect 80 percent of DCIS cases. Some
of these cases will eventually develop into invasive breast cancer.
It is not possible to predict which cases of DCIS will progress to invasive
cancer. Therefore, DCIS usually is removed surgically. In the past, DCIS was
often treated with a mastectomy,
but breast-conserving therapy
(breast-sparing surgery
plus radiation therapy) is now standard practice for many women with DCIS.
Tamoxifen
may also be used. Women who have been diagnosed with DCIS should talk with
their doctor to make an informed decision about treatment.
- How much does a mammogram cost?
The cost of screening mammograms varies by state and by facility, and can
depend on insurance coverage. However, most states have laws requiring health
insurance companies to reimburse all or part of the cost of screening mammograms.
Women are encouraged to contact their mammogram facility or their health insurance
company for information about cost and coverage.
All women age 40 and older with Medicare
can get a screening mammogram each year. Medicare will also pay for one baseline
mammogram for a woman between the ages of 35 and 39. There is no deductible
requirement for this benefit, but Medicare beneficiaries have to pay 20 percent
of the Medicare-approved amount. Information about Medicare coverage is available
at http://www.medicare.gov on the Internet,
or through the Medicare Hotline at 1–800–MEDICARE (1–800–633–4227).
For the hearing impaired, the telephone number is 1–877–486–2048.
- How can women who are low-income or uninsured
obtain a screening mammogram?
Some state and local health programs and employers provide mammograms free
or at low cost. For example, the Centers for Disease Control and Prevention
(CDC) coordinates the National Breast and Cervical
Cancer Early Detection Program. This program provides screening services,
including clinical breast exams and mammograms, to low-income, uninsured women
throughout the United States and in several U.S. territories. Contact information
for local programs is available on the CDC’s Web site at http://apps.nccd.cdc.gov/cancercontacts/nbccedp/contacts.asp
or by calling the CDC at 1–800–CDC–INFO (1–800–232–4636).
Information about low-cost or free mammography screening programs is also
available through NCI’s Cancer
Information Service (CIS) at 1–800–4–CANCER (1–800–422–6237).
Women can also check with their local hospital, health department, women’s
center, or other community groups to find out how to access low-cost or free
mammograms.
- Where can women get high-quality mammograms?
Women can get high-quality mammograms in breast clinics, hospital radiology
departments, mobile vans, private radiology offices, and doctors’ offices.
The Mammography Quality Standards Act (MQSA) is a Federal law designed to
ensure that mammograms are safe and reliable. Through the MQSA, all mammography
facilities in the United States must meet stringent quality standards, be
accredited by the Food
and Drug Administration (FDA), and be inspected annually. The FDA ensures
that mammography facilities across the country meet MQSA standards. These
standards apply to the following people at the mammography facility:
- The technologist who takes the mammogram.
- The radiologist
who interprets the mammogram.
- The medical physicist who tests the mammography equipment.
Women can ask their doctors or staff at the mammography facility about FDA
certification before making an appointment. All mammography facilities are
required to display their FDA certificate. Women should look for the MQSA
certificate at the mammography facility and check its expiration date. MQSA
regulations also require mammography facilities to give patients an easy-to-read
report on the results of their mammogram.
Information about local FDA-certified mammography facilities is available
through the CIS at 1–800–4–CANCER (1–800–422–6237).
Also, a list of these facilities is on the FDA’s Web site at http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfMQSA/mqsa.cfm
on the Internet.
- What should women with breast implants
do about screening mammograms?
Women with breast implants should continue to have mammograms. (A woman who
had an implant following breast cancer surgery should ask her doctor whether
a mammogram of the reconstructed breast is necessary.) It is important to
inform the mammography facility about breast implants when scheduling a mammogram.
The technician and radiologist must be experienced in x-raying patients with
breast implants. Implants can hide some breast tissue, making it more difficult
for the radiologist to detect an abnormality on the mammogram. If the technician
performing the procedure is aware a woman has breast implants, steps can be
taken to make sure that as much breast tissue as possible can be seen on the
mammogram.
- What is digital
mammography? How is it different from conventional (film) mammography?
Both digital and conventional mammography use x-rays to produce an image
of the breast; however, conventional mammography stores the image directly
on film, whereas digital mammography takes an electronic image of the breast
and stores it directly in a computer. This allows the recorded information
to be enhanced, magnified, or manipulated for further evaluation. The difference
between conventional mammography and digital mammography is like the difference
between a traditional film camera and a digital camera. Aside from the difference
in how the image is recorded and stored, there is no other difference between
the two.
Because digital mammography allows a radiologist to electronically adjust,
store, and retrieve digital images, digital mammography may offer the following
advantages over conventional mammography:
- Health care providers can share image files electronically, making long-distance
consultations with other mammography specialists easier.
- Subtle differences between normal and abnormal tissues may be more easily
noted.
- The number of follow-up procedures needed may be fewer.
- Fewer repeat images may be needed, reducing the exposure to radiation.
In January 2000, the FDA approved the use of digital mammography in the United
States. In September 2005, preliminary results from a large clinical trial
that compared digital mammography to film
mammography were published (1). These findings showed
no difference between digital and film mammograms in detecting breast cancer
in the general population of women in the trial. However, the researchers
concluded that women with dense breasts who are premenopausal
or perimenopausal
(women who had their last menstrual period within 12 months of their mammograms)
or who are younger than age 50 may benefit from having a digital rather than
a film mammogram.
Some health care providers recommend that women who have a very high risk
of breast cancer, such as those with BRCA1 or BRCA2 gene
alterations, have digital mammograms instead of conventional mammograms; however,
studies showing that digital mammograms are superior to conventional mammograms
for these women are lacking.
Digital mammography can be done only in facilities that are certified to
practice conventional mammography and have received FDA approval to offer
digital mammography. The procedure for having a mammogram with a digital system
is the same as with conventional mammography.
- What other technologies are being developed
for breast cancer screening?
NCI is supporting the development of several new technologies to detect breast
tumors. This research ranges from methods being developed in research labs
to those that have reached clinical trials. Efforts to improve conventional
mammography include digital mammography (see Question 15),
magnetic
resonance imaging (MRI), and positron
emission tomography (PET scanning).
In addition to imaging technologies, NCI-supported scientists
are exploring methods to detect markers
(genetic traits) of breast cancer in blood, urine,
or nipple aspirates (fluid from the breast) that may serve as early warning
signals for breast cancer. The NCI fact sheet Improving Methods for Breast
Cancer Detection and Diagnosis provides more information about technologies
that are under development for breast cancer screening and diagnosis. This
fact sheet is available at http://www.cancer.gov/cancertopics/factsheet/Detection/breast-cancer
on the Internet.
- How is NCI supporting efforts to find better
ways to prevent and treat breast cancer?
NCI conducts and supports ongoing breast cancer research that ranges from
basic science through the full spectrum of clinical care.
- Basic research—Researchers are trying to identify
the causes of breast cancer, including the role of gene changes or variations
in addition to changes in BRCA1 and BRCA2. Scientists
are also investigating how hormonal, dietary, and environmental factors
might contribute to the development of breast cancer.
- Prevention—As a result of NCI-supported research,
the drugs tamoxifen and raloxifene
have been approved by the FDA to reduce the risk of developing breast cancer
in women who are at high risk for the disease; tamoxifen can be used by
both premenopausal and postmenopausal
women, whereas raloxifene is appropriate for postmenopausal women only.
Currently, researchers are looking for additional ways to prevent breast
cancer in women who are at increased risk. They are studying other preventive
agents and how changes in diet,
physical activity, nutrition,
and environmental factors may lead to a reduced risk of developing breast
cancer.
- Early detection and diagnosis—Several studies are
seeking better ways to detect and diagnose breast cancer, so women can receive
treatment sooner.
- Treatment—Numerous studies are being conducted
to find more effective and less toxic
treatments for breast cancer, better ways to deal with the symptoms of this
disease and the side
effects of its treatment, and new approaches to improve the quality
of life of breast cancer patients and survivors.
In the HTML version of this fact sheet on NCI's Web site (http://www.cancer.gov/cancertopics/factsheet/Detection/mammograms),
the text below links to searches of clinical trials or female breast cancer
prevention, screening, and treatment. The trials are included in the clinical
trials database that can be searched at http://www.cancer.gov/clinicaltrials/search
on the Internet.
Current NCI-supported clinical trials for female breast cancer prevention
Current NCI-supported clinical trials for female breast cancer screening
Current NCI-supported clinical trials for female breast cancer treatment
Additional information about clinical trials is available from NCI's Cancer
Information Service (1-800-4-CANCER) or on the main clinical trials page of
NCI's Web site at http://www.cancer.gov/clinicaltrials
on the Internet.
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