Also called: Screening Mammography, Mammography, Diagnostic Mammography, Digital Mammograms

Reviewed By:
Mark Oren, M.D., FACP
Martin E. Liebling, M.D., FACP


A mammogram, or mammography, is a specialized x-ray procedure used to create detailed images of the breast. It is used to detect changes in the breast tissue, such as thickened tissue lumps or calcification that may indicate the presence of breast cancer, and finding them early can significantly increase a patient’s odds of survival. Mammography can detect some abnormalities between one and three years before they can be felt.

Mammograms can be ordered by a physician to detect a variety of breast disorders, ranging from cysts (fluid-filled sacs) to cancer. Mammograms may be ordered to:

  • Screen for a condition. Used when women have no signs or symptoms of breast cancer or other breast abnormalities.

  • Diagnose a condition. Used to check for cancer based on signs, symptoms or other test results.

Mammograms use special imaging machines  and are usually performed on outpatients. The test is administered by a radiation technologist, usually someone who has been specially trained for mammograms. The mammogram images are stored on films that are reviewed by a physician (physician mammographer) and often additional cancer specialists, for any signs of abnormalities.

Mammogram rates increased steadily from the 1980s until 2000, when they leveled off. However, beginning in 2005, studies showed that mammogram rates dropped significantly, especially among groups of women with previously high screening rates. In a similar timeframe (beginning in 2003), reports of new cases of breast cancer also dropped, according to the American Cancer Society (ACS). Although this information has been hailed as good news, it may be related to cancers undetected because of the decline in screening mammograms.

Mammograms are currently the most effective way to screen for early breast cancer. The ACS recommends that women age 40 and older have a mammogram every year, while the National Cancer Institute recommends mammograms every one to two years for this age group.

About mammograms

A mammogram is a special x-ray of the breasts used to diagnose abnormalities, including breast cancer. It is the single most effective way to detect cancer in its early stages, when it is most treatable. Mammography can find abnormalities between one and three years before they can be felt. When breast cancer is detected before it has spread to the lymph nodes, patients have a five-year survival rate of 98 percent, according to the American Cancer Society (ACS). Only one or two mammograms out of every 1,000 leads to a diagnosis of cancer.

Mammograms detect cancer by revealing tissues that are denser than those in the normal tissues of the breast. They can detect lesions as small as 0.5 centimeters (0.2 inches). Most lumps cannot be felt until they are at least 1 centimeter (0.4 inches). 

Mammograms can detect calcium deposits in the breast. Appearing as small, white dots on film, these can be the result of cell secretions, cell debris, inflammation, trauma, previous radiation or foreign bodies. Calcium deposits that are tiny and irregularly shaped (microcalcifications) are often associated with cancer. They may appear alone or in clusters. When found, they may prompt a follow-up mammogram or a biopsy. Microcalcifications are the most common sign on a mammogram of ductal carcinoma in situ (early noninvasive cancer confined to the breast ducts).

Larger, coarser deposits called macrocalcifications are sometimes the result of a benign (noncancerous) condition called fibroadenoma. This is a common tumor of the female breast. Aging of the breast arteries, old injuries and inflammation are also common causes of macrocalcification. Macrocalcifications are not cancerous and are found in half of women over age 50 and in one in 10 women under 50, according to the ACS.

Masses or lumps can occur with or without calcifications. While they are sometimes cancerous, they are often cysts (a noncancerous collection of fluid) or benign tumors, such as fibroadenomas. The presence of a cyst needs to be confirmed with either a fine needle aspiration or a breast ultrasound. Suspected cancerous masses usually require a biopsy for confirmation. As with calcifications, masses can be caused by benign breast conditions or by breast cancer. The size, shape and edges (margins) of the mass help the physician determine whether or not it is cancer. The physician will also look for:

  • Dense areas that appear in only one breast

  • Dense areas or microcalcifications that were not seen in the patient’s last mammogram

  • Distorted areas (which may suggest tumors that have invaded nearby tissues)

Sometimes, dense areas in mammograms indicate tissue packed with glands that make calcifications and masses harder to detect. On the other hand, dense areas may also indicate cancer itself.

If suspicious areas are found, a physician may order an ultrasound or needle aspiration to help determine whether the mass is solid (such as in a tumor) or is a fluid-filled cyst. If nipple discharge is present, a physician may order an x-ray exam called galactography, a procedure in which a fine plastic tube is placed into the opening of the nipple’s duct and a contrast material is injected into the duct.

Patients may obtain mammograms from many different facilities, including hospitals, clinics, physicians’ offices and x-ray or imaging centers. Mobile units also provide mammograms during screening events at shopping malls, community centers and offices. A federal law called the Mammography Quality Standards Act (MQSA) regulates mammography. Under MQSA, all mammography personnel and facilities, including mobile units, in the United States must be accredited and be certified by the Food and Drug Administration (FDA). In addition, these facilities must pass annual inspections and display their FDA certificate in a location visible to patients.

Although mammograms are the most effective way to screen for breast cancer, studies have shown that many women fail to get them regularly. Common reasons provided by women included fear, embarrassment and most often, cost. Mammogram costs vary according to a patient’s insurance coverage. Medicaid and private insurance typically cover the full cost of an annual screening mammogram on women over 40. However, Medicare only covers 80 percent of the cost, forcing women to pay the remaining 20 percent. Many states offer mammograms at low or no cost to women who qualify based on income.

The ACS recommends that women age 40 and older have a mammogram every year, while the National Cancer Institute (NCI) recommends mammograms every one to two years for this age and risk group. Women younger than 40 may be advised to get mammograms if they have other risk factors for breast cancer.

Women at higher risk of breast cancer should consult their physician about when to begin scheduling mammograms, and how often to have the procedure. Risk factors that may increase the scheduling of mammograms include:

  • Personal history of breast cancer

  • Breast cancer in mother or sister

  • Family history or personal history of gene abnormalities associated with cancer (e.g., BRCA1 or BRCA2 genes)

  • No pregnancies or first pregnancy after age 35

  • Early onset of menstruation

  • Late menopause

  • History of atypical findings or prior breast biopsies

  • Treatment with radiation therapy to the chest or neck before age 30

Mammograms are most effective when used to examine the breasts of women over age 40. As a woman ages, breast tissue increasingly is replaced with fat. By the time a woman reaches menopause, there are usually just a few strands of breast tissue left. Fat appears gray on mammograms, making it easy to see the white spots that indicate abnormalities. In contrast, the breasts of younger women are usually too dense to provide good mammogram images.

Mammogram rates have decreased in the past several years, especially among groups of women with previously high screening rates, according to the American Cancer Society (ACS). Experts are concerned about the decline, especially because it coincides with a decline in breast cancer rates. Although some of the decline in cases may be attributed to better and earlier screening, some cases may be undetected because women are not getting screening mammograms.

In many cases, an ultrasound or magnetic resonance imaging (MRI) is a good substitute for women in the older age group. MRI in conjunction with a mammogram also may be recommended for women who are at high risk for the disease. The ACS recommends women in their 20s and 30s have a clinical breast exam by a health professional every three years.

Limitations of mammograms

Mammography tests are not perfect. Only the part of the breast that extends from the body can be imaged. This makes it easier to get an accurate picture of a larger breast than a smaller breast. In addition, the periphery of the breast does not appear on the image at all. It also may be difficult to detect abnormalities that exist in the breast tissue adjacent to the chest wall.

Breast cancers are most likely to develop in dense tissue, where they are most difficult to detect. Mammograms can result in false negative readings (particularly in younger women, who have dense breast tissue) or false positive readings. In a false negative reading, dense breast tissue may obscure a tumor and the mammogram may fail to detect its presence. In a false positive, the mammogram appears abnormal when, in fact, no cancer is present.
Other factors that can significantly impact the accuracy of the test include:

  • Quality of film used.

  • Experience and skill of the technician and radiologist. The appearance of breast tissue on a mammogram varies significantly from woman to woman. A skilled technician may be able to obtain more accurate films. The skill and experience of the radiologist can make a difference in how accurately the mammogram is analyzed.

  • Breast density. Breast tissue becomes fattier and has fewer glands as women age, which results in mammograms that are easier to interpret. Breast tissue that is denser, as in younger women, makes it more difficult to detect abnormalities.

In addition, mammography does not detect all cancers. In some cases, such as the armpit or chest wall, the area of the body is not easily viewable. However, a lump may be felt in a breast exam. In other cases, the cancer may be too small to be revealed by this test. Up to 20 percent of breast cancers are missed by mammograms, according to the National Cancer Institute. For this reason, mammograms and physical exams are considered to be complementary techniques.

Mammograms of women with breast implants can be very difficult to interpret. The x-rays used in mammography do not easily penetrate silicone or saline implants, making it harder to image overlying and underlying breast tissue. 

Women with implants are likely to have four additional images taken. Known as implant displacement (ID) views, they involve pushing the implant against the chest wall while the breast is pulled over it. This provides better imaging of the front part of the breast. This technique is not as effective in women who have experienced the formation of scar tissue around the implants. ID images are most successful in women whose implants are placed underneath the chest muscle.

Women who have had breast-conserving surgery, or lumpectomy, will need to continue to schedule regular mammograms, while women who have had their breast removed will no longer need mammograms of that area. Patients should consult with their physician about how breast cancer surgery might impact their need for future mammograms.

Types and differences of mammograms

Physicians order mammograms to detect or diagnose breast abnormalities ranging from cysts to cancer. Mammograms may be performed for different purposes and include:

  • Screening mammogram. Used when women have no signs or symptoms of breast cancer. The goal is to detect cancers in the earliest state. A screening mammogram typically requires two x-rays of each breast.
    • Cranial-caudal. Examines the breasts from above.
    • Mediolateral-oblique. Examines the breasts from an angle that includes breast tissue extending to the armpit.
  • Diagnostic mammogram. Used to check for cancer due to symptoms or other test results, including screening mammograms. Diagnostic mammograms may include more images and may concentrate on specific areas of the breast. Changes in the breast that may indicate the need for a mammogram include:
    • Lumps
    • Pain
    • Nipple thickening, retraction or discharge
    • Change in breast size or shape, or change in overlying skin
  • After a woman has been diagnosed with breast cancer, she will continue to receive regular diagnostic mammograms.

    Diagnostic mammograms are also used to evaluate the breasts of women with implants, which sometimes can obscure the presence of the disease.

Before the mammogram test

In preparing for a mammogram, women can gather information that may be valuable to the physician. Information to report includes:

  • Problems with breasts
  • Past breast biopsies or surgeries
  • Whether the patient has implants
  • Whether the patient is pregnant or nursing
  • Whether the patient is using hormone replacement therapy or taking hormones or treatment for any breast disorders
  • Timing of menstrual cycle
  • Whether the patient has started menopause

Patients who schedule an exam at a new facility should be sure to bring prior mammograms and accompanying reports with them. It is important to bring the original mammogram films, rather than copies. Federal law requires that all mammography facilities give patients their original mammograms when needed.

During a mammogram, a woman’s breasts will be compressed. Patients should not schedule these exams when breasts are likely to be tender, such as the week before or week of a menstrual period. The week after a menstrual period is often the time when a woman’s breasts are least tender.

On the day of the test, women should not apply any of the following under their arms or to their breasts:

  • Deodorants and antiperspirants
  • Powders
  • Lotions
  • Creams
  • Perfumes

Some of these cosmetics can cause densities on mammograms, leading to confusion during the reading of the mammogram.

Women with a history of breast pain (mastalgia) or tenderness should consider taking an over-the-counter pain medication about one hour prior to a mammogram.

After the mammogram test

After the radiologist is satisfied with the images, the patient is allowed to dress and resume her daily activities without restriction.

One or more physician mammographers will examine the x-ray images and look for abnormalities. Masses that appear round and smooth are more likely to be cysts (fluid-filled sac) or fibroadenoma (noncancerous tumor caused by high levels of estrogen). On the other hand, abnormalities that contain jagged, distinct, radiating strands that pull inward are more likely to be cancer.

A physician mammographer usually gives a preliminary verbal report to the patient at the time of the mammogram. However, an official written report may not be completed for several weeks. The completed report will be sent to the patient’s primary physician. Women with a history of breast cancer  should have the report sent to their cancer care team physicians, including the  surgeon, medical oncologist and radiation oncologist.

Federal law requires all facilities offering mammograms to provide the patient with an easy-to-understand, written explanation of the findings within 30 days. Patients who have not received a report within this time frame should contact their physician.

The American College of Radiology has developed a method of describing the findings of mammograms called the breast imaging reporting and data system (BIRADS). This is broken into two major divisions:

Incomplete assessment

Category 0: Additional imaging evaluation and/or comparison to prior mammograms neededPossible abnormality may not be completely seen or defined and will need more tests, such as use of spot compression, magnification views, special mammogram views or ultrasound.

Complete assessment

Category 1: NegativeNo significant abnormality to report. Breasts appear the same (symmetrical) with no masses, architectural distortion or suspicious calcifications.
Category 2: Benign (Noncancerous)Also a negative mammogram, but with description of a finding known to be benign, such as benign calcifications, intramammary lymph nodes or calcified fibroadenomas. This ensures others viewing the mammogram will not misinterpret benign finding as suspicious. Finding is recorded in the mammogram report for use in future mammogram assessments.
Category 3: Probably benign – follow-up suggestedFindings have a very high probability (greater than 98%) of being benign. Findings are not expected to change. Follow-up with repeat imaging usually done in six months and regularly thereafter until finding is known to be stable (usually at least two years). Procedure helps avoid unnecessary biopsies while allowing for early diagnosis of a cancer should suspicious area change.
Category 4: Suspicious abnormality – biopsy suggestedFindings could be cancer, with sufficient concern to recommend biopsy. Findings in this category have a wide range of suspicion levels. Some – though not all – physicians may divide category further:
4A: finding with low suspicion of being cancerous

4B: finding with intermediate suspicion of being cancerous

4C: finding of moderate concern of being cancerous, but not as high as Category 5
Category 5: Highly suggestive of malignancy – appropriate action necessaryFindings look like and have high probability (at least 95%) of being cancer. Biopsy is strongly recommended.
Category 6: Confirmed Malignancy – Appropriate Action Should Be TakenUsed for findings on mammogram already determined to be cancerous by a previous biopsy.

In some cases, a woman may have to take her imaging films with her for a scheduled visit to her surgeon or oncologist. She should notify the imaging technician of her intention to take the films so they can be prepared.  Women should take precautions in not damaging or losing the films because they are records of valuable information for her care. In addition, she should be sure to return the films to the imaging center for safekeeping after the physician is finished with them.

Treatments that may follow mammogram

If a mammogram shows suspicious results, another mammogram or biopsy of breast tissue may follow. If a woman is diagnosed with breast cancer, her physician will formulate a treatment plan. Treatments that may follow a breast cancer diagnosis may include any of the following:

  • Lumpectomy. Treatment in which a lump in the breast and some normal tissue surrounding it are removed. Also known as breast conservation therapy, it is a form of surgery that removes a cancer while allowing a woman to preserve the natural appearance of her breast.

  • Mastectomy. Surgical removal of one or both breasts, usually as a lifesaving measure after a diagnosis of advanced breast cancer.

  • Chemotherapy and/or radiation therapy. Chemotherapy uses a single drug or combination of drugs to destroy cancer cells and keep them from growing, dividing and spreading. Radiation therapy uses an energy called ionizing radiation to kill cancer cells and shrink tumors. Either or both of these treatments may be used before surgery to shrink the size of a tumor, or after surgery to kill any remaining cancer cells. 

The recommendations for follow-up mammograms may vary. Some physicians recommend that women who have a lumpectomy receive mammography of the treated breast every six months for two to three years. Other physicians believe an annual exam is adequate.

Women who have total, modified radical or radical mastectomies do not need further screening on the affected side or sides.

Ongoing research regarding mammograms

There are several new techniques being developed to help physicians both detect abnormalities and to distinguish whether they are cancerous or noncancerous.

  • Digital tomosynthesis. This technique uses x-rays of each breast from different angles which are combined to create a three-dimensional image of the breast. The ability to look at cross-sections of the breast can reduce the problem of overlapping tissues that often appears on traditional mammograms. It is hoped that this technology eventually will improve detection of breast cancer in the early stages, while also reducing the number of unnecessary biopsies. However, at this point, digital tomosynthesis is available only for research purposes.

  • Full-field digital mammography (FFDM). Recently approved by the U.S. Food and Drug Administration (FDA), this technique involves taking digital images of the breast. Digital images are captured electronically and can be viewed on a computer. Their magnification, brightness and contrast can be adjusted and enhanced to better reveal abnormalities. These images can be transmitted electronically to other locations for additional opinions from other experts. Initial studies indicate that digital mammography may be more effective in detecting cancer in women under the age of 50, premenopausal and perimenopausal women and women with dense breasts. However, research continues on whether digital mammography is more effective, overall, than conventional mammography for the detection of breast cancer.  Digital mammography is not yet widely available in the United States.

  • Computer-aided detection and diagnosis (CAD). Computers can help detect information from a mammogram that a radiologist might miss. A machine converts the standard x-ray mammogram to a digital image, which is analyzed by a computer. The computer displays the image with markers that indicate potential trouble spots. The FDA has approved some of these devices. Studies of CAD have produced mixed results. Some physicians believe these devices can provide valuable insights, while others complain that the machines can falsely identify abnormalities, leading to unnecessary biopsies. Recent studies have shown that CAD can improve the detection rate of smaller tumors.

  • New scanning devices. Research continues into new scanning techniques that may be more useful in identifying tumors in denser breasts and in areas closer to the chest wall or underarms.

Questions for your doctor about mammograms

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about mammograms:

  1. How often do I need a mammogram?
  2. Can you recommend a reliable facility for mammography?
  3. What can be detected on a mammogram?
  4. What is the difference between a screening mammogram and a diagnostic mammogram?
  5. Do I need to tell the technician anything for my mammogram?
  6. I have had breast cancer in the past. Do I need to do anything different for my mammograms?
  7. How soon and from whom will I learn of the results of my mammogram?
  8. How can I be sure my reports will be sent to my doctors in a timely manner?
  9. If there is something suspicious on my mammogram, what follow-up tests may be performed?
  10. If I need a visit with an oncologist or surgeon, how do I obtain my films?
  11. Based on my medical history, how often should I have a mammogram?
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