A mammogram is an x-ray picture of the breast. A special x-ray machine is used to perform the exam.
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-ray pictures, or images, of each breast. The x-ray images 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 the disease has been found. This type of mammogram is called a diagnostic mammogram. Besides a lump, signs of breast cancer can include breast pain, thickening of the skin of the breast, nipple discharge, or a change in breast size or shape; however, these signs may also be signs of benign conditions. A diagnostic mammogram can also 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.
Digital mammography, also called full-field digital mammography (FFDM), is a mammography system in which the x-ray film is replaced by electronics that convert x-rays into mammographic pictures of the breast. These systems are similar to those found in digital cameras and their efficiency enables better pictures with a lower radiation dose. These images of the breast are transferred to a computer for review by the radiologist and for long term storage. The patient’s experience during a digital mammogram is similar to having a conventional film mammogram.
Because digital mammography allows a radiologist to adjust, store, and retrieve digital images electronically, digital mammography may offer the following advantages over conventional mammography:
- Health care providers can share image files electronically, making long-distance consultations between radiologists and breast surgeons easier.
- Subtle differences between normal and abnormal tissues may be more easily noted.
- Fewer follow-up procedures may be needed.
- Fewer repeat images may be needed, reducing the exposure to radiation.
How Screening and Diagnostic Mammography Differ?
What should women with breast implant do about screening Mammogram?
Diagnostic mammography takes longer than screening mammography because more x-rays are needed 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.
Early detection of breast cancer with screening mammography means that treatment can be started earlier in the course of the disease, possibly before it has spread. Results from randomized clinical trials and other studies show that screening mammography can help reduce the number of deaths from breast cancer among women ages 40 to 74, especially for those over age 50.
The benefits need to be balanced against the harms, including:
False-positive results. False-positive results occur when radiologists decide mammograms are abnormal but no cancer is actually present. All abnormal mammograms should be followed up with additional testing (diagnostic mammograms, ultrasound, and/or biopsy) to determine whether cancer is present.
False-positive results are more common for 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, menopausal hormone therapy).
False-positive mammogram results can lead to anxiety and other forms of psychological distress in affected women. The additional testing required to rule out cancer can also be costly and time consuming and can cause physical discomfort.
Overdiagnosis and overtreatment. Screening mammograms can find cancers and cases of ductal carcinoma in situ (DCIS, a noninvasive tumor in which abnormal cells that may become cancerous build up in the lining of breast ducts) that need to be treated. However, they can also find cancers and cases of DCIS that will never cause symptoms or threaten a woman’s life, leading to “overdiagnosis” of breast cancer. Treatment of these latter cancers and cases of DCIS is not needed and leads to “overtreatment.” Overtreatment exposes women unnecessarily to the adverse effects associated with cancer therapy.
Because doctors often cannot distinguish cancers and cases of DCIS that need to be treated from those that do not, they are all treated.
False-negative results. False-negative results occur when mammograms appear normal even though breast cancer is present. Overall, screening mammograms miss about 20 percent of breast cancers that are present at the time of screening.
The main cause of false-negative results is high breast density. Breasts contain both dense tissue (i.e., glandular tissue and connective tissue, together known as fibroglandular tissue) and fatty tissue. Fatty tissue appears dark on a mammogram, whereas fibroglandular tissue appears as white areas. Because fibroglandular tissue and tumors have similar density, tumors can be harder to detect in women with denser breasts.
False-negative results occur more often among younger women than among older women because younger women are more likely to have dense breasts. As a woman ages, her breasts usually become more fatty, and false-negative results become less likely. False-negative results can lead to delays in treatment and a false sense of security for affected women.
Some of the cancers missed by screening mammograms can be detected by clinical breast exams (physical exams of the breast done by a health care provider).
Finding cancer early does not always reduce a woman’s chance of dying from breast cancer. Even though mammograms can detect malignant tumors that cannot be felt, treating a small tumor does not always mean that the woman will not die from the cancer. A fast-growing or aggressive cancer may have already spread to other parts of the body before it is detected. Women with such tumors live a longer period of time knowing that they likely have a fatal disease.
In addition, screening mammograms may not help prolong the life of a woman who is suffering from other, more life-threatening health conditions.
Radiation exposure. Mammograms require very small doses of radiation. The risk of harm from this radiation exposure is extremely low, but repeated x-rays have the potential to cause cancer. The benefits of mammography, however, nearly always outweigh the potential harm from the radiation exposure. Nevertheless, women should talk with their health care providers about the need for each x-ray. In addition, they should always let their health care provider and the x-ray technician know if there is any possibility that they are pregnant, because radiation can harm a growing fetus.
Getting a high-quality screening mammogram and having a clinical breast exam on a regular basis are the most effective ways to detect breast cancer early.
Checking one’s own breasts for lumps or other unusual changes is called a breast self-exam, or BSE. This type of exam cannot replace regular screening mammograms or clinical breast exams. In clinical trials, BSE alone was not found to help reduce the number of deaths from breast cancer.
Although regular BSE is not specifically recommended for breast cancer screening, many women choose to examine their own breasts. Women who do so should remember that breast changes can occur because of pregnancy, aging, or menopause; during menstrual cycles; or when 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.
Women with breast implants should continue to have mammograms. (A woman who had an implant following a mastectomy should ask her doctor whether a mammogram of the reconstructed breast is necessary.) It is important to let the mammography facility know about breast implants when scheduling a mammogram. The technician and radiologist must be experienced in performing mammography on women who have 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 that 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. A special technique called implant displacement views may be used.