What is Mammography?
Mammography is a specific type of imaging that uses a low-dose x-ray system to examine breasts. A mammography exam, called a mammogram, is used to aid in the diagnosis of breast diseases in women.
An x-ray (radiograph) is a painless medical test that helps physicians diagnose and treat medical conditions. Radiography involves exposing a part of the body to a small dose of ionizing radiation to produce pictures of the inside of the body. X-rays are the oldest and most frequently used form of medical imaging.
Today, the x-ray machines used for mammograms produce lower energy x-rays. These x-rays do not go through tissue as easily as those used for routine chest x-rays or x-rays of the arms or legs, and this improves the image quality. Mammograms today expose the breast to much less radiation compared with those in the past.
Screening mammograms look for signs of cancer
Screening mammogram are x-ray exams of the breasts that are used for women who have no breast symptoms. The goal of a screening mammogram is to find breast cancer when it’s too small to be felt by a woman or her doctor. Finding small breast cancers early (before they have grown and spread) with a screening mammogram greatly improves a woman’s chance for successful treatment.
Diagnostic mammograms investigate possible problems
A woman with a breast problem (for instance, a lump or nipple discharge) or an abnormal area found in a screening mammogram typically gets a diagnostic mammogram. It’s still an x-ray exam of the breast, but it’s done for a different purpose.
During a diagnostic mammogram, additional pictures are taken to carefully study the area of concern. In most cases, special pictures are enlarged to make a small area of suspicious breast tissue bigger and easier to evaluate. Other types of x-ray pictures can be done, too, depending on the type of problem and where it is in the breast.
Recommendations for screening mammography:
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.
The National Cancer Institute (NCI) adds that women who have had breast cancer and those who are at increased risk due to a genetic history of breast cancer should seek expert medical advice about whether they should begin screening before age 40 and about the frequency of screening.
Diagnostic mammography is used to evaluate a patient with abnormal clinical findings—such as a breast lump or lumps—that have been found by the woman or her doctor. Diagnostic mammography may also be done after an abnormal screening mammography in order to determine the cause of the area of concern on the screening exam.
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 a history of breast cancer (especially if they were diagnosed before age 50).
- Certain breast changes on biopsy—A diagnosis of atypical hyperplasia (a noncancerous condition in which cells have abnormal features and are increased in number) or lobular carcinoma in situ (LCIS) (abnormal cells found in the lobules of the breast) increases a woman’s risk of breast cancer. Women who have had two or more breast biopsies for other benign conditions also have an increased chance of developing breast cancer. This increased risk is due to the condition that led to the biopsy, and not to the biopsy itself.
- Genetic alterations (changes)—Specific alterations in certain genes (BRCA1, BRCA2, and others) increase the risk of breast cancer. These alterations 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 periods before age 12 or went through menopause after age 55 are at an increased risk of developing breast cancer. Women who have their first child after age 30 or who never have a child are at an 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 —Breasts appear dense on a mammogram if they contain many glands and ligaments (called dense tissue), and do not have much fatty tissue. Because breast cancers tend to develop in the dense tissue of the breast (not in the fatty tissue), older women who have mostly dense tissue on a mammogram are at an increased risk of breast cancer. Abnormalities in dense breasts can be more difficult to detect on a mammogram.
- Radiation therapy (“x-ray therapy”)—Women who had radiation therapy to the chest (including the breasts) before age 30 are at an increased risk of developing breast cancer throughout their lives. This includes women treated for Hodgkin’s disease. Studies show that the younger a woman was when she received her treatment, the higher her risk of developing breast cancer later in life.
- 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 suggest that the more alcohol a woman drinks, the greater her risk of breast cancer.
What are some of the limitations of screening mammograms?
- Finding cancer does not always mean saving lives—Even though mammography can detect tumors that cannot be felt, finding a small tumor does not always mean that a woman’s life will be saved. Mammography may not help a woman with a fast-growing or aggressive cancer that has already spread to other parts of her body before being detected.
- False negatives —False negatives occur when mammograms appear normal even though breast cancer is present. Overall, 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 (and therefore less dense), and breast cancers become easier to detect with screening mammograms.
- False positives —false positives occur when mammograms are read by a radiologist as 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).
What is the best method of detecting breast cancer as early as possible?
Getting a high-quality 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. Like any test, mammograms have both benefits and limitations. For example, some cancers cannot be detected by a mammogram, but may be found by breast examination.
Checking one’s own breasts for lumps or other unusual changes is called breast self-exam (BSE). Studies so far have not shown that BSE alone reduces the number of deaths from breast cancer. BSE should not take the place of routine clinical breast exams and mammograms.