What is screening?
General Information About Breast Cancer
Breast Cancer Screening
Risks of Breast Cancer Screening
Get More Information From NCI
Changes to This Summary (12/19/2008)
Questions or Comments About This Summary
About PDQ

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.

See the PDQ summaries on Breast Cancer Prevention ¹ and Breast Cancer Treatment ² for information about prevention, diagnosis, and treatment of breast cancer.

General Information About Breast Cancer

Key Points for This Section

Breast cancer is a disease in which malignant (cancer) cells form in the tissues of the breast. Breast cancer is the second leading cause of death from cancer in American women. Age and health history can affect the risk of developing 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.

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Anatomy of the breast, showing lymph nodes and lymph vessels.

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.

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.

See the PDQ summary on Genetics of Breast and Ovarian Cancer ³ for more information about family history and breast cancer screening.

Breast Cancer Screening

Key Points for This Section

Tests are used to screen for different types of cancer. Two tests are commonly used by health care providers to screen for breast cancer: Mammogram Clinical breast exam (CBE) If a lump or other change is found by mammogram or clinical breast exam, follow-up tests may be needed. Other screening tests are being studied in clinical trials. MRI (magnetic resonance imaging) Tissue sampling

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 ⁴.

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.

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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 ⁴.

Risks of Breast Cancer Screening

Key Points for This Section

Screening tests have risks. The risks of breast cancer screening tests include the following: Finding breast cancer may not improve health or help a woman live longer. False-negative test results can occur. False-positive test results can occur. Mammograms expose the breast to radiation. The risks and benefits of screening for breast cancer may be different for different groups of people.

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.
• In women 35 years or younger who go to the doctor for breast symptoms, mammogram results may not be helpful in managing their care.

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.

Get More Information From NCI

Call 1-800-4-CANCER

For more information, U.S. residents may call the National Cancer Institute's (NCI's) Cancer Information Service toll-free at 1-800-4-CANCER (1-800-422-6237) Monday through Friday from 9:00 a.m. to 4:30 p.m. Deaf and hard-of-hearing callers with TTY equipment may call 1-800-332-8615. The call is free and a trained Cancer Information Specialist is available to answer your questions.

Chat online

The NCI's LiveHelp® ⁵ online chat service provides Internet users with the ability to chat online with an Information Specialist. The service is available from 9:00 a.m. to 11:00 p.m. Eastern time, Monday through Friday. Information Specialists can help Internet users find information on NCI Web sites and answer questions about cancer.

Write to us

For more information from the NCI, please write to this address:

NCI Public Inquiries Office

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6116 Executive Boulevard, MSC8322

Bethesda, MD 20892-8322

Search the NCI Web site

The NCI Web site ⁶ 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 our “Best Bets” search box in the upper right hand corner of each Web page. The results that are most closely related to your search term will be listed as Best Bets at the top of the list of search results.

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 ⁷. These materials can also be ordered by telephone from the Cancer Information Service toll-free at 1-800-4-CANCER (1-800-422-6237), TTY at 1-800-332-8615.

Changes to This Summary (12/19/2008)

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 ⁸. We can respond only to email messages written in English.

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 ⁶. 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 ⁹. 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); TTY at 1-800-332-8615.

Glossary Terms

Not normal. An abnormal lesion or growth may be cancerous, premalignant (likely to become cancer), or benign.

A chemical substance found in beer, wine, and liquor. Alcohol is also found in some medicines, mouthwashes, essential oils (scented liquid taken from plants), and household products.

Feelings of fear, dread, and uneasiness that may occur as a reaction to stress. A person with anxiety may sweat, feel restless and tense, and have a rapid heart beat. Extreme anxiety that happens often over time may be a sign of an anxiety disorder.

The area of dark-colored skin on the breast that surrounds the nipple.

The underarm or armpit.

Not cancerous. Benign tumors may grow larger but do not spread to other parts of the body.

The removal of cells or tissues for examination by a pathologist. The pathologist may study the tissue under a microscope or perform other tests on the cells or tissue. There are many different types of biopsy procedures. The most common types include: (1) incisional biopsy, in which only a sample of tissue is removed; (2) excisional biopsy, in which an entire lump or suspicious area is removed; and (3) needle biopsy, in which a sample of tissue or fluid is removed with a needle. When a wide needle is used, the procedure is called a core biopsy. When a thin needle is used, the procedure is called a fine-needle aspiration biopsy.

A tube through which the blood circulates in the body. Blood vessels include a network of arteries, arterioles, capillaries, venules, and veins.

Glandular organ located on the chest. The breast is made up of connective tissue, fat, and breast tissue that contains the glands that can make milk. Also called mammary gland.

Cancer that forms in tissues of the breast, usually the ducts (tubes that carry milk to the nipple) and lobules (glands that make milk). It occurs in both men and women, although male breast cancer is rare.

A term for diseases in which abnormal cells divide without control. Cancer cells can invade nearby tissues and can spread to other parts of the body through the blood and lymph systems. There are several main types of cancer. Carcinoma is cancer that begins in the skin or in tissues that line or cover internal organs. Sarcoma is cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue. Leukemia is cancer that starts in blood-forming tissue such as the bone marrow, and causes large numbers of abnormal blood cells to be produced and enter the blood. Lymphoma and multiple myeloma are cancers that begin in the cells of the immune system. Central nervous system cancers are cancers that begin in the tissues of the brain and spinal cord.

A flexible tube used to deliver fluids into or withdraw fluids from the body.

The individual unit that makes up the tissues of the body. All living things are made up of one or more cells.

An exam of the breast performed by a health care provider to check for lumps or other changes.

A type of research study that tests how well new medical approaches work in people. These studies test new methods of screening, prevention, diagnosis, or treatment of a disease. Also called clinical study.

The process of identifying a disease, such as cancer, from its signs and symptoms.

A method used to identify a disease.

The amount of medicine taken, or radiation given, at one time.

In medicine, a tube or vessel of the body through which fluids pass.

A noninvasive condition in which abnormal cells are found in the lining of a breast duct. The abnormal cells have not spread outside the duct to other tissues in the breast. In some cases, ductal carcinoma in situ may become invasive cancer and spread to other tissues, although it is not known at this time how to predict which lesions will become invasive. Also called DCIS and intraductal carcinoma.

A method used to collect cells from milk ducts in the breast. 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. The cells are checked under a microscope. Ductal lavage may be used in addition to clinical breast examination and mammography to detect breast cancer.

A type of hormone made by the body that helps develop and maintain female sex characteristics and the growth of long bones. Estrogens can also be made in the laboratory. They may be used as a type of birth control and to treat symptoms of menopause, menstrual disorders, osteoporosis, and other conditions.

A test result that indicates that a person does not have a specific disease or condition when the person actually does have the disease or condition.

A test result that indicates that a person has a specific disease or condition when the person actually does not have the disease or condition.

A record of a person's current and past illnesses, and those of his or her parents, brothers, sisters, children, and other family members. A family history shows the pattern of certain diseases in a family, and helps to determine risk factors for those and other diseases.

The removal of tissue or fluid with a thin needle for examination under a microscope. Also called FNA biopsy.

Liquid.

One of many chemicals made by glands in the body. Hormones circulate in the bloodstream and control the actions of certain cells or organs. Some hormones can also be made in the laboratory.

Invasion and multiplication of germs in the body. Infections can occur in any part of the body and can spread throughout the body. The germs may be bacteria, viruses, yeast, or fungi. They can cause a fever and other problems, depending on where the infection occurs. When the body’s natural defense system is strong, it can often fight the germs and prevent infection. Some cancer treatments can weaken the natural defense system.

Transmitted through genes that have been passed from parents to their offspring (children).

Cancer that has spread beyond the layer of tissue in which it developed and is growing into surrounding, healthy tissues. Also called infiltrating cancer.

A portion of an organ, such as the liver, lung, breast, thyroid, or brain.

A small lobe or a subdivision of a lobe.

Cancer that forms in tissues of the lung, usually in the cells lining air passages. The two main types are small cell lung cancer and non-small cell lung cancer. These types are diagnosed based on how the cells look under a microscope.

The clear fluid that travels through the lymphatic system and carries cells that help fight infections and other diseases. Also called lymphatic fluid.

A rounded mass of lymphatic tissue that is surrounded by a capsule of connective tissue. Lymph nodes filter lymph (lymphatic fluid), and they store lymphocytes (white blood cells). They are located along lymphatic vessels. Also called lymph gland.

A thin tube that carries lymph (lymphatic fluid) and white blood cells through the lymphatic system. Also called lymphatic vessel.

An x-ray of the breast.

The use of x-rays to create a picture of the breast.

Periodic discharge of blood and tissue from the uterus. From puberty until menopause, menstruation occurs about every 28 days when a woman is not pregnant.

A procedure in which radio waves and a powerful magnet linked to a computer are used to create detailed pictures of areas inside the body. These pictures can show the difference between normal and diseased tissue. MRI makes better images of organs and soft tissue than other scanning techniques, such as computed tomography (CT) or x-ray. MRI is especially useful for imaging the brain, the spine, the soft tissue of joints, and the inside of bones. Also called magnetic resonance imaging, NMRI, and nuclear magnetic resonance imaging.

Having an abnormally high, unhealthy amount of body fat.

A part of the body that performs a specific function. For example, the heart is an organ.

PDQ is an online database developed and maintained by the National Cancer Institute. Designed to make the most current, credible, and accurate cancer information available to health professionals and the public, PDQ contains peer-reviewed summaries on cancer treatment, screening, prevention, genetics, complementary and alternative medicine, and supportive care; a registry of cancer clinical trials from around the world; and directories of physicians, professionals who provide genetics services, and organizations that provide cancer care. Most of this information, and more specific information about PDQ, can be found on the NCI's Web site at http://www.cancer.gov/cancertopics/pdq. Also called Physician Data Query.

A type of hormone made by the body that plays a role in the menstrual cycle and pregnancy. Progesterone can also be made in the laboratory. It may be used as a type of birth control and to treat menstrual disorders, infertility, symptoms of menopause, and other conditions.

The overall enjoyment of life. Many clinical trials assess the effects of cancer and its treatment on the quality of life. These studies measure aspects of an individual’s sense of well-being and ability to carry out various activities.

Energy released in the form of particle or electromagnetic waves. Common sources of radiation include radon gas, cosmic rays from outer space, medical x-rays, and energy given off by a radioisotope (unstable form of a chemical element that releases radiation as it breaks down and becomes more stable).

The use of high-energy radiation from x-rays, gamma rays, neutrons, protons, and other sources to kill cancer cells and shrink tumors. Radiation may come from a machine outside the body (external-beam radiation therapy), or it may come from radioactive material placed in the body near cancer cells (internal radiation therapy). Systemic radiation therapy uses a radioactive substance, such as a radiolabeled monoclonal antibody, that travels in the blood to tissues throughout the body. Also called irradiation and radiotherapy.

A doctor who specializes in creating and interpreting pictures of areas inside the body. The pictures are produced with x-rays, sound waves, or other types of energy.

Something that may increase the chance of developing a disease. Some examples of risk factors for cancer include age, a family history of certain cancers, use of tobacco products, certain eating habits, obesity, lack of exercise, exposure to radiation or other cancer-causing agents, and certain genetic changes.

A picture of structures inside the body. Scans often used in diagnosing, staging, and monitoring disease include liver scans, bone scans, and computed tomography (CT) or computerized axial tomography (CAT) scans and magnetic resonance imaging (MRI) scans. In liver scanning and bone scanning, radioactive substances that are injected into the bloodstream collect in these organs. A scanner that detects the radiation is used to create pictures. In CT scanning, an x-ray machine linked to a computer is used to produce detailed pictures of organs inside the body. MRI scans use a large magnet connected to a computer to create pictures of areas inside the body.

Checking for disease when there are no symptoms. Since screening may find diseases at an early stage, there may be a better chance of curing the disease. Examples of cancer screening tests are the mammogram (breast), colonoscopy (colon), Pap smear (cervix), and PSA blood level and digital rectal exam (prostate). Screening can also include checking for a person’s risk of developing an inherited disease by doing a genetic test.

X-rays of the breasts taken to check for breast cancer in the absence of signs or symptoms.

When referring to a medical test, sensitivity refers to the percentage of people who test positive for a specific disease among a group of people who have the disease. No test has 100% sensitivity because some people who have the disease will test negative for it (false negatives).

A problem that occurs when treatment affects healthy tissues or organs. Some common side effects of cancer treatment are fatigue, pain, nausea, vomiting, decreased blood cell counts, hair loss, and mouth sores.

Cancer that forms in tissues of the skin. There are several types of skin cancer. Skin cancer that forms in melanocytes (skin cells that make pigment) is called melanoma. Skin cancer that forms in basal cells (small, round cells in the base of the outer layer of skin) is called basal cell carcinoma. Skin cancer that forms in squamous cells (flat cells that form the surface of the skin) is called squamous cell carcinoma. Skin cancer that forms in neuroendocrine cells (cells that release hormones in response to signals from the nervous system) is called neuroendocrine carcinoma of the skin. Most skin cancers form in older people on parts of the body exposed to the sun or in people who have weakened immune systems.

A computer picture of areas inside the body created by bouncing high-energy sound waves (ultrasound) off internal tissues or organs. Also called ultrasonogram.

The extent of a cancer in the body. Staging is usually based on the size of the tumor, whether lymph nodes contain cancer, and whether the cancer has spread from the original site to other parts of the body.

A procedure to remove or repair a part of the body or to find out whether disease is present. An operation.

An indication that a person has a condition or disease. Some examples of symptoms are headache, fever, fatigue, nausea, vomiting, and pain.

A group or layer of cells that work together to perform a specific function.

An abnormal mass of tissue that results when cells divide more than they should or do not die when they should. Tumors may be benign (not cancerous), or malignant (cancerous). Also called neoplasm.

A procedure in which high-energy sound waves (ultrasound) are bounced off internal tissues or organs and make echoes. The echo patterns are shown on the screen of an ultrasound machine, forming a picture of body tissues called a sonogram. Also called ultrasonography.

A type of high-energy radiation. In low doses, x-rays are used to diagnose diseases by making pictures of the inside of the body. In high doses, x-rays are used to treat cancer.