Ultrasound vs. Mammogram: What's the Difference?

This page explains how breast ultrasound and mammograms differ, and when they are used together.

Mammograms and ultrasounds both look at breast tissue. They work in different ways and are good at different things. A mammogram uses low-dose x-rays. It is used for breast cancer screening. An ultrasound uses sound waves and no radiation. It is often used to take a closer look at one specific area. The two are not an either-or choice. They are sometimes used together.

A mammogram is an x-ray picture of the breast. It uses a low dose of radiation. It is the test NCI describes for breast cancer screening, and NCI says it can find abnormal tissue, including cancer, sometimes before symptoms appear. Screening mammograms are done on a schedule your care team recommends. NCI says mammography is more likely to miss cancer in women with dense breasts.

An ultrasound uses sound waves to make pictures of the tissue inside the breast. It does not use radiation. MedlinePlus says it is usually ordered when more information is needed after other tests, or as a stand-alone test. Examples include a lump found on an exam, an abnormal mammogram, or nipple discharge. It can help tell a solid mass from a fluid-filled cyst.

The two tests answer different questions. A mammogram may show an area that needs more detail, and an ultrasound can help make it clearer. NCI says mammography is more likely to miss cancer in women with dense breasts, so ask your team whether you need anything more. Depending on the results, more tests may be advised, and sometimes that includes a biopsy.

NCI describes mammography as the test used for breast cancer screening. MedlinePlus describes ultrasound as a test ordered when more information is needed. Ask your team whether an ultrasound is meant to add to your mammogram or to replace it, and how often you need each.

Questions for your care team:

• Which test or combination do you advise, and why?
• Is this for routine screening or to look at a specific finding?
• What might happen next, depending on the result?
• When will we go over the results together?

Screening is for people with no symptoms. A new change in your breast is a different matter, and it should not wait for your next scheduled mammogram.

• Call your care team the same day if your breast becomes red, warm, swollen or painful, especially with a fever. This can be a sign of an infection that needs treatment.
• Call your care team within a day or two if you notice any new change in a breast — a lump, discharge from the nipple, a change in the skin, or a change in the shape of the breast.

NCI says many benign breast conditions are not linked to higher breast cancer risk, but it advises contacting your doctor about any breast change. They need to be looked at rather than watched at home.

• National Cancer Institute — Mammograms Fact Sheet
• MedlinePlus — Breast ultrasound
• National Cancer Institute — Benign and Precancerous Breast Conditions
• National Cancer Institute — Breast Cancer Diagnosis