What are the limitations of mammograms for detecting breast cancer?

Dr. Deanna J. Attai, MD

While mammograms are very important for detecting breast cancer, they are not perfect. Approximately 10 to 20 percent of breast cancers will not show up on a mammogram. If a woman has dense breast tissue (which is more likely in younger women), as many as 40 percent of breast cancers can be hidden on a mammogram.

Newer forms of mammography such as tomosynthesis (3D mammography) can be helpful in women with dense breast tissue. Ultrasound is also sometimes used as a supplement to mammography, especially in younger women.

Dr. Laurie R. Margolies, MD
Diagnostic Radiologist

The limitations of mammography often relate to breast density. Many women with dense breasts are younger although there are women in their 80s with dense breasts. The normal dense glandular tissue can hide a cancer. 3D mammography—tomosynthesis—was approved by the FDA in 2011 and may help mammographers find cancers in women with dense breasts. A landmark study called DMIST also showed that digital mammography helps overcome some of the limitations of mammography. Digital mammography as opposed to analog mammography was shown to find more cancers in young women under 50, women with dense breasts and pre or peri-menopausal women.

Although mammography is not perfect, it has been shown to save lives and screening mammograms are recommended for normal risk women beginning at age 40. If you think you are at higher risk—maybe because of family history, for example - you should ask your doctor about starting screening mammography earlier or adding supplemental imaging exams.

Dr. Anne C. Hoyt, MD
Diagnostic Radiologist

Mammography is a great, proven test, but it’s not perfect. It doesn’t find every single breast cancer. We all know someone who had a mammogram that didn’t detect her breast cancer. This is usually due to the density of the breast tissue. A small breast cancer would be easy to see in a fatty breast, whereas that same tumor might be entirely obscured in a dense breast. This is why density is so important. Breast density varies with age and hormonal status; however, some women's breasts remain dense, even after menopause.

A mammogram cannot prove that an abnormal area is cancer. To confirm whether cancer is present, a small amount of tissue must be removed and looked at under a microscope. This procedure is called a biopsy. You should also be aware that mammograms are done to find breast cancer that cannot be felt. If you have a breast lump, you should have it checked by your doctor and consider having it biopsied even if your mammogram result is normal.

For some women, such as those with breast implants, additional pictures may be needed. Breast implants make it harder to see breast tissue on standard mammograms, but additional x-ray pictures with implant displacement and compression views can be used to more completely examine the breast tissue.

Mammograms are not perfect at finding breast cancer. They do not work as well in younger women, usually because their breasts are dense and can hide a tumor. This may also be true for pregnant women and women who are breast-feeding. Since most breast cancers occur in older women, this is usually not a major concern.

However, this can be a problem for young women who are at high risk for breast cancer (due to gene mutations, a strong family history of breast cancer, or other factors) because they often develop breast cancer at a younger age. For this reason, the American Cancer Society now recommends MRI scans in addition to mammograms for screening in these women.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.