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Breast Cancer Screening (PDQ®): Screening - Patient Information [NCI]

This information is produced and provided by the National Cancer Institute (NCI). The information in this topic may have changed since it was written. For the most current information, contact the National Cancer Institute via the Internet web site at http://cancer.gov or call 1-800-4-CANCER.

Breast Cancer Screening

What is screening?

Screening is looking for cancer before a person has any symptoms. This can help find cancer at an early stage. When abnormal tissue or cancer is found early, it may be easier to treat. By the time symptoms appear, cancer may have begun to spread.

Scientists are trying to better understand which people are more likely to get certain types of cancer. They also study the things we do and the things around us to see if they cause cancer. This information helps doctors recommend who should be screened for cancer, which screening tests should be used, and how often the tests should be done.

It is important to remember that your doctor does not necessarily think you have cancer if he or she suggests a screening test. Screening tests are given when you have no cancer symptoms.

If a screening test result is abnormal, you may need to have more tests done to find out if you have cancer. These are called diagnostic tests.

General Information About Breast Cancer

Breast cancer is a disease in which malignant (cancer) cells form in the tissues of the breast.

The breast is made up of lobes and ducts. Each breast has 15 to 20 sections called lobes, which have many smaller sections called lobules. Lobules end in dozens of tiny bulbs that can produce milk. The lobes, lobules, and bulbs are linked by thin tubes called ducts.
Drawing of female breast anatomy showing the lymph nodes, nipple, areola, chest wall, ribs, muscle, fatty tissue, lobe, and ducts.
Anatomy of the female breast. The nipple and areola are shown on the outside of the breast. The lymph nodes, lobes, lobules, ducts, and other parts of the inside of the breast are also shown.

Each breast also contains blood vessels and lymph vessels. The lymph vessels carry an almost colorless fluid called lymph. Lymph vessels lead to organs called lymph nodes. Lymph nodes are small bean-shaped structures that are found throughout the body. They filter substances in lymph and help fight infection and disease. Clusters of lymph nodes are found near the breast in the axilla (under the arm), above the collarbone, and in the chest.

See the following PDQ summaries for more information about breast cancer:

  • Breast Cancer Prevention
  • Breast Cancer Treatment
  • Genetics of Breast and Ovarian Cancer

Breast cancer is the second leading cause of death from cancer in American women.

Women in the United States get breast cancer more than any other type of cancer except for skin cancer. Breast cancer is second only to lung cancer as a cause of cancer death in women. Breast cancer occurs in men also, but the number of cases is small.

Age and health history can affect the risk of developing breast cancer.

Anything that increases your chance of getting a disease is called a risk factor. Having a risk factor does not mean that you will get cancer; not having risk factors doesn't mean that you will not get cancer. People who think they may be at risk should discuss this with their doctor. Risk factors for breast cancer include:

  • Older age.
  • Early age at menarche (menstruation).
  • Older age at first birth or never having given birth.
  • A personal history of breast cancer or benign (noncancer) breast disease.
  • A mother or sister with breast cancer.
  • Treatment with radiation therapy to the breast/chest.
  • Breast tissue that is dense on a mammogram.
  • Taking hormones such as estrogen and progesterone.
  • Obesity.
  • Drinking alcoholic beverages.
  • Being white.

NCI's Breast Cancer Risk Assessment Tool uses a woman's risk factors to estimate her risk for breast cancer during the next five years and up to age 90. This online tool is meant to be used by a health care provider. For more information on breast cancer risk, call 1-800-4-CANCER.

Breast Cancer Screening

Tests are used to screen for different types of cancer.

Some screening tests are used because they have been shown to be helpful both in finding cancers early and in decreasing the chance of dying from these cancers. Other tests are used because they have been shown to find cancer in some people; however, it has not been proven in clinical trials that use of these tests will decrease the risk of dying from cancer.

Scientists study screening tests to find those with the fewest risks and most benefits. Cancer screening trials also are meant to show whether early detection (finding cancer before it causes symptoms) decreases a person's chance of dying from the disease. For some types of cancer, the chance of recovery is better if the disease is found and treated at an early stage.

Clinical trials that study cancer screening methods are taking place in many parts of the country. Information about ongoing clinical trials is available from the NCI Web site.

Two tests are commonly used by health care providers to screen for breast cancer:

Mammogram

A mammogram is an x-ray of the breast. This test may find tumors that are too small to feel. A mammogram may also find ductal carcinoma in situ, abnormal cells in the lining of a breast duct, which may become invasive cancer in some women. The ability of a mammogram to find breast cancer may depend on the size of the tumor, the density of the breast tissue, and the skill of the radiologist. Mammograms are less likely to find breast tumors in women younger than 50 years than in older women. This may be because younger women have denser breast tissue that appears white on a mammogram. A tumor also appears white on a mammogram, which makes it hard to find.
Photograph shows the right breast positioned between the plates of a mammography machine.
Mammography of the right breast.

Clinical breast exam (CBE)

A clinical breast exam is an exam of the breast by a doctor or other health professional. The doctor will carefully feel the breasts and under the arms for lumps or anything else that seems unusual.

It is important to know how your breasts usually look and feel. If you feel any lumps or notice any other changes, talk to your doctor.

If a lump or other change is found by mammogram or clinical breast exam, follow-up tests may be needed.

If a lump or anything else that seems abnormal is found using one of these 2 tests, ultrasound may be used to learn more. Ultrasound is not used by itself as a screening test for breast cancer. This is a procedure in which high-energy sound waves (ultrasound) are bounced off internal tissues or organs and make echoes. The echoes form a picture of body tissues called a sonogram.

Other screening tests are being studied in clinical trials.

MRI (magnetic resonance imaging)

MRI is a procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the body. This procedure is also called nuclear magnetic resonance imaging (NMRI). MRI does not use any x-rays.

In women with a high inherited risk of breast cancer, screening trials of MRI breast scans have shown that MRI is more sensitive than mammography for finding breast tumors. It is common for MRI breast scan results to appear abnormal even though no cancer is present. Screening studies of breast MRI in women at high inherited risk are ongoing.

In women at average risk for breast cancer, MRI scans may be done to help with diagnosis. MRI may be used to:

  • Study lumps in the breast that remain after surgery or radiation therapy.
  • Study breast lumps or enlarged lymph nodes found during a clinical breast exam or a breast self-exam that were not seen on mammography or ultrasound.
  • Plan surgery for patients with known breast cancer.

Tissue sampling

Breast tissue sampling is taking cells from breast tissue to examine under a microscope. Abnormal cells in breast fluid have been linked to an increased risk of breast cancer in some studies. Scientists are studying whether breast tissue sampling can be used to find breast cancer at an early stage or predict the risk of developing breast cancer. Three methods of tissue sampling are under study:

  • Fine-needle aspiration: A thin needle is inserted into the breast tissue around the areola (darkened area around the nipple) to withdraw cells and fluid.
  • Nipple aspiration: The use of gentle suction to collect fluid through the nipple. This is done with a device similar to the breast pumps used by nursing women.
  • Ductal lavage: A hair-size catheter (tube) is inserted into the nipple and a small amount of salt water is released into the duct. The water picks up breast cells and is removed.

Screening clinical trials are taking place in many parts of the country. Information about ongoing clinical trials is available from the NCI Web site.

Risks of Breast Cancer Screening

Screening tests have risks.

Decisions about screening tests can be difficult. Not all screening tests are helpful and most have risks. Before having any screening test, you may want to discuss the test with your doctor. It is important to know the risks of the test and whether it has been proven to reduce the risk of dying from cancer.

The risks of breast cancer screening tests include the following:

Finding breast cancer may not improve health or help a woman live longer.

Screening may not help you if you have fast-growing breast cancer or if it has already spread to other places in your body. Also, some breast cancers found on a screening mammogram may never cause symptoms or become life-threatening. When such cancers are found, treatment would not help you live longer and may instead cause serious treatment-related side effects. At this time, it is not possible to be sure which breast cancers found by screening will cause symptoms and which breast cancers will not.

False-negative test results can occur.

Screening test results may appear to be normal even though breast cancer is present. A woman who receives a false-negative test result (one that shows there is no cancer when there really is) may delay seeking medical care even if she has symptoms.

One in 5 cancers may be missed by mammography. False-negatives occur more often in younger women than in older women because the breast tissue of younger women is more dense. The size of the tumor, the rate of tumor growth, the level of hormones, such as estrogen and progesterone, in the woman's body, and the skill of the radiologist can also affect the chance of a false-negative result.

False-positive test results can occur.

Screening test results may appear to be abnormal even though no cancer is present. A false-positive test result (one that shows there is cancer when there really isn't) can cause anxiety and is usually followed by more tests (such as biopsy), which also have risks.

Most abnormal test results turn out not to be cancer. 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 take hormones, such as estrogen and progesterone. The skill of the doctor also can affect the chance of a false-positive result.

Mammograms expose the breast to radiation.

Being exposed to radiation is a risk factor for breast cancer. The risk of developing breast cancer from radiation exposure, such as screening mammograms or x-rays, is greater with higher doses of radiation and in younger women. For women older than 40 years, the benefits of an annual screening mammogram may be greater than the risks from radiation exposure.

The risks and benefits of screening for breast cancer may be different for different groups of people.

The benefits of breast cancer screening may vary among age groups:

  • In women who have a life expectancy of 5 years or less, finding and treating early stage breast cancer may reduce their quality of life without helping them live longer.
  • In women older than 65 years, the results of a screening test may lead to more diagnostic tests and anxiety while waiting for the test results. Also, the breast cancers found are usually not life-threatening.
  • It has not been shown that women benefit from starting mammography at younger than 40 years.

Routine breast cancer screening is advised for women who have had radiation treatment to the chest, especially at a young age. The benefits and risks of mammograms and MRIs for these women are not known. There is no information on the benefits or risks of breast cancer screening in men.

No matter how old you are, if you have risk factors for breast cancer you should ask for medical advice about when to begin having mammograms and how often to be screened.

Changes to This Summary (08 / 18 / 2011)

The PDQ cancer information summaries are reviewed regularly and updated as new information becomes available. This section describes the latest changes made to this summary as of the date above.

Editorial changes were made to this summary.

Questions or Comments About This Summary

If you have questions or comments about this summary, please send them to Cancer.gov through the Web site's Contact Form. We can respond only to email messages written in English.

Get More Information From NCI

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Search the NCI Web site

The NCI Web site provides online access to information on cancer, clinical trials, and other Web sites and organizations that offer support and resources for cancer patients and their families. For a quick search, use the search box in the upper right corner of each Web page. The results for a wide range of search terms will include a list of "Best Bets," editorially chosen Web pages that are most closely related to the search term entered.

There are also many other places to get materials and information about cancer treatment and services. Hospitals in your area may have information about local and regional agencies that have information on finances, getting to and from treatment, receiving care at home, and dealing with problems related to cancer treatment.

Find Publications

The NCI has booklets and other materials for patients, health professionals, and the public. These publications discuss types of cancer, methods of cancer treatment, coping with cancer, and clinical trials. Some publications provide information on tests for cancer, cancer causes and prevention, cancer statistics, and NCI research activities. NCI materials on these and other topics may be ordered online or printed directly from the NCI Publications Locator. These materials can also be ordered by telephone from the Cancer Information Service toll-free at 1-800-4-CANCER (1-800-422-6237).

About PDQ

PDQ is a comprehensive cancer database available on NCI's Web site.

PDQ is the National Cancer Institute's (NCI's) comprehensive cancer information database. Most of the information contained in PDQ is available online at NCI's Web site. PDQ is provided as a service of the NCI. The NCI is part of the National Institutes of Health, the federal government's focal point for biomedical research.

PDQ contains cancer information summaries.

The PDQ database contains summaries of the latest published information on cancer prevention, detection, genetics, treatment, supportive care, and complementary and alternative medicine. Most summaries are available in two versions. The health professional versions provide detailed information written in technical language. The patient versions are written in easy-to-understand, nontechnical language. Both versions provide current and accurate cancer information.

The PDQ cancer information summaries are developed by cancer experts and reviewed regularly.

Editorial Boards made up of experts in oncology and related specialties are responsible for writing and maintaining the cancer information summaries. The summaries are reviewed regularly and changes are made as new information becomes available. The date on each summary ("Date Last Modified") indicates the time of the most recent change.

PDQ also contains information on clinical trials.

A clinical trial is a study to answer a scientific question, such as whether a method of finding cancer earlier can help people to live longer. Trials are based on past studies and what has been learned in the laboratory. Each trial answers certain scientific questions in order to find new and better ways to help cancer patients and those who are at risk for cancer. During screening clinical trials, information is collected about the effects of a new screening method and how well it works. If a clinical trial shows that a new method is better than one currently being used, the new method may become "standard." People who are at high risk for a certain type of cancer may want to think about taking part in a clinical trial.

Listings of clinical trials are included in PDQ and are available online at NCI's Web site. Descriptions of the trials are available in health professional and patient versions. Many cancer doctors who take part in clinical trials are also listed in PDQ. For more information, call the Cancer Information Service 1-800-4-CANCER (1-800-422-6237).

Last Revised: 2011-08-18


If you want to know more about cancer and how it is treated, or if you wish to know about clinical trials for your type of cancer, you can call the NCI's Cancer Information Service at 1-800-422-6237, toll free. A trained information specialist can talk with you and answer your questions.


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