Breast ultrasound

This page was reviewed under our medical and editorial policy by

Daniel Liu, MD, Plastic and Reconstructive Surgeon

This page was updated on March 8, 2024.

Breast ultrasound (also called sonography) is a safe, painless, non-invasive imaging test that uses sound waves to produce pictures of the interior of the breast. It shows breast tissue changes that may not appear on a mammogram and helps to confirm the type of mass, if one is present.

Ultrasound in breast cancer diagnosis

Breast ultrasound is not typically part of routine breast cancer screening tests. Instead, it’s used to diagnose abnormalities that appear on other tests or breast lumps that may be felt but don’t show up on a mammogram.

Mammogram vs. breast ultrasound

Breast cancer screening typically starts with a mammogram that uses low-dose X-rays to detect changes in breast tissue.

If any areas appear suspicious or unclear, ultrasound testing is often used to detect if the mass is a noncancerous cyst or a solid mass that needs further examination.

Ultrasound-guided breast biopsy

If a breast biopsy is needed, an ultrasound may be used to guide the needle to the specific area of the breast or lymph nodes under the arm. Cells are then extracted and sent to the lab for testing to see if they are cancerous.

How a breast ultrasound is done

Breast ultrasound involves a computer, a video monitor and a wand-like, handheld transducer that both transmits sound waves and records the resulting echoes. First, a water-based gel is applied to the area of the breast to be examined and sometimes to the end of the transducer as well. The transducer is then lightly pressed onto the area and moved over the skin. The recorded echoes from the sound waves bouncing off of breast tissue become pictures on the computer screen.

The procedure typically takes 30 minutes or less, and patients shouldn’t feel any pain.

Some imaging centers offer automated breast ultrasound (ABUS), which uses a much larger transducer to cover almost the entire breast. ABUS may be recommended for patients whose breasts are more dense, those with abnormal test results and people experiencing breast symptoms. A second ultrasound with a handheld transducer may be needed to get more images of any areas that appear abnormal.

Breast ultrasound results

The results of mammograms, breast ultrasounds and breast magnetic resonance imaging (MRI) are all interpreted according to a standard system called the Breast Imaging Reporting and Data System (BI-RADS).

BI-RADS sorts the results into categories numbered 0 through 6.

  • Category 0 indicates unclear results that require additional testing.
  • Categories 1 through 3 reflect findings that are most likely not cancer.
  • Category 4 shows a possibility of cancer.
  • Category 5 shows a high likelihood of cancer.
  • Category 6 is designated for cancer that was already diagnosed with a biopsy.

BI-RADS also categorizes breast tissue according to density using letters A through D, with A being the least dense and D being extremely dense.

What does breast cancer look like on an ultrasound?

Both cysts and masses (areas of abnormal breast tissue) typically appear as dark spots in the images. However, breast cysts are usually darker with round edges. A cancerous mass often has a slightly lighter color with an irregular shape. A breast ultrasound may distinguish between fluid-filled and solid masses, but sometimes more information is needed. A biopsy of the suspicious area may be needed to confirm whether it’s malignant (cancerous) or benign (noncancerous).

The mass’s shape, size and edges all factor into the chances of it being cancerous.

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Show references

American College of Radiology and the Radiological Society of North America (2022, Nov. 1). Breast Ultrasound. https://www.radiologyinfo.org/en/info/breastus

American Cancer Society (2022, Jan. 14). Breast ultrasound. https://www.cancer.org/cancer/types/breast-cancer/screening-tests-and-early-detection/breast-ultrasound.html

American Cancer Society (2023, March 28). Breast Density and Your Mammogram Report. https://www.cancer.org/cancer/types/breast-cancer/screening-tests-and-early-detection/mammograms/breast-density-and-your-mammogram-report.html

American Cancer Society (2022, Nov. 17). Cancer during pregnancy. https://www.cancer.org/cancer/managing-cancer/making-treatment-decisions/cancer-during-pregnancy.html

American Society of Clinical Oncology (2022, October). Breast cancer: Diagnosis. https://www.cancer.net/cancer-types/breast-cancer/diagnosis

American Cancer Society (2022, January 14). Mammogram Basics. https://www.cancer.org/cancer/types/breast-cancer/screening-tests-and-early-detection/mammograms/mammogram-basics.html

City of Hope (2022, February 8). Breast Biopsy. https://www.cancercenter.com/cancer-types/breast-cancer/diagnosis-and-detection/breast-biopsy

City of Hope (2022, September 20). What are BI-RADS categories? https://www.cancercenter.com/cancer-types/breast-cancer/diagnosis-and-detection/mammography/results-bi-rads

National Breast Cancer Foundation. Breast Cancer Ultrasound. https://nbcf.org.au/about-breast-cancer/detection-and-awareness/breast-cancer-ultrasound/