Breast Ultrasound vs. Mammography: Which Is Best?

Though mammograms can miss tumors, they provide more information

A breast ultrasound or sonogram is not the same as a mammogram. Both are imaging tests that can be used to look for breast cancer. A mammogram is the gold standard for breast cancer detection, but a breast ultrasound is a complementary test that can help identify specific changes in the breast.

Since each test complements the other, healthcare providers may use breast ultrasounds with mammograms for breast cancer screening and diagnosis.

This article reviews the differences between breast ultrasounds and mammograms. You will learn about the benefits, limitations, and risks of each type of imaging test as well as other options for diagnosing breast cancer.

Limitations Ultrasound in Breast Cancer Screening
Verywell / JR Bee

Purpose of Breast Ultrasounds vs. Mammograms

A mammogram is an X-ray of the breasts. Mammograms are the most effective breast cancer screening test.

They can take multiple pictures of the breast and identify calcifications (calcium deposits within breast tissue). In addition, mammograms are important for diagnosing and following up after breast cancer.

A breast ultrasound or sonogram is generally used for diagnostic reasons. For example, an ultrasound is most helpful when evaluating dense breasts or a suspicious lump found on a mammogram.

A breast ultrasound is good at distinguishing a benign fluid-filled cyst from a solid mass. An ultrasound of the breast can help define a mass found by touch, even if it does not appear on a mammogram.

Breast Ultrasound vs. Mammograms: How They Work

A big difference between a mammogram and a breast ultrasound is how they work. Mammograms use low-dose radiation to X-ray the breasts, while ultrasounds use sound waves.

  • Radiation: Although you will be exposed to small amounts of radiation during a mammogram, the benefits of having one usually outweigh the risks. However, if you're pregnant, radiation from a mammogram can harm the fetus.
  • Sound waves: The sound waves generated by an ultrasound create an echo that produces the ultrasound image. No radiation is emitted during a breast ultrasound.

Does Mammogram Radiation Raise Breast Cancer Risk?

A 2016 study in the Annals of Internal Medicine found that although 125 women out of 100,000 may experience radiation-induced breast cancer from mammograms, 968 deaths could be prevented by early detection with a mammogram.

Breast Ultrasound vs. Mammogram: Image Quality

The quality of the images from a breast ultrasound and a mammogram are also different.

  • Mammograms: If a screening mammogram identifies a suspicious area in the breast, you will likely need a diagnostic mammogram. A diagnostic mammogram takes more pictures than a routine screening mammogram and focuses on the affected area.
  • Ultrasounds: A breast ultrasound cannot spot microcalcifications in the breast. Although calcifications are not always a sure sign of breast cancer, many early breast cancers are suspected because calcifications are seen.

Recent studies suggest that people who have dense breasts could benefit from a mammogram plus fast breast magnetic resonance imaging (fast breast MRI). The combination of tests may produce fewer false positives than mammography and ultrasound alone.

In addition, fast breast MRI seems to be equal to conventional MRIs, which are the best test for finding breast cancer. Though they are good, they are expensive and usually only offered to high-risk patients. Since fast breast MRI testing is relatively new, it is not available at every facility that offers breast cancer screenings.

Limitations of Mammograms and Breast Ultrasounds

Both mammograms and breast ultrasounds have limitations. However, there are more limitations to breast ultrasounds.

Breast ultrasounds:

  • Cannot examine deep breast tissue in some people: In people with very large breasts, a mammogram is better at looking for abnormalities that are deep in the breast tissue.
  • Screening tests may not evaluate the axillary lymph nodes (armpits): While an ultrasound screening test might miss abnormal axillary lymph nodes, an ultrasound done for a clinical concern will examine the axilla for signs of cancer. Evaluation of the axillary lymph nodes is divided into three levels: the lower, middle, and upper part of the armpit. When breast cancer is in the axillary lymph nodes they become swollen and larger than normal. If breast cancer is found in the axillary lymph nodes it could mean the disease has metastasized (spread) to other parts of the body.

That said, mammograms and ultrasounds are both subject to user error. One study found that radiologists missed 10% to 30% of breast cancers seen on mammograms. Additionally, the operator's skill level can significantly affect the accuracy of a breast ultrasound result.

When Are Breast Ultrasounds Needed?

Mammogram remains the gold standard for breast cancer screening. People at average risk for breast cancer can begin yearly mammograms at the age of 40. At 55, mammograms can be spaced out every other year.

Breast ultrasounds are typically done as a complement or additional test after a mammogram. In people who have dense breast tissue, for example, an ultrasound can sometimes identify malignancies that aren't visible on a mammogram image.

Ultrasound as an annual test (instead of a mammogram) is not currently recommended for people who aren't at risk for breast cancer. This is because there isn't enough evidence to prove that the benefits outweigh the harms.

For example, a breast ultrasound could be false positive, indicating that you may have cancer when you don't. That means you might need to go back for a biopsy or other tests. If you don't have cancer, these tests can cause unnecessary stress.

Comparisons

Ultrasounds and mammograms each have different strengths and weaknesses. You may need a breast ultrasound if your provider finds something unusual on your mammogram. For example, when your mammogram shows a lesion on your breast, an ultrasound can help determine if it is a cyst or a solid mass.

Mammogram vs. Ultrasound

Mammogram
  • Uses a small amount of radiation

  • Can't distinguish between a cyst and a solid mass

  • Not as good at spotting abnormalities in people with dense breast tissue

  • Good at spotting calcifications

  • Different views can give the radiologist a look at the entire breast

  • Can be used to find suspicious areas deeper inside the breast

  • Can view the axillary lymph nodes

  • Typically used for breast cancer screening

Breast Ultrasound
  • Does not use radiation

  • Can help distinguish between solid masses and cysts

  • Better at spotting abnormalities in people with dense breast tissue

  • Much less effective at finding calcifications

  • Cannot view the entire breast

  • Cannot view deep breast tissue

  • Cannot view the axillary lymph nodes

  • Typically used for diagnosing abnormalities found during screening

Risk Factors

Having a family history of breast cancer or inherited genetic mutations like breast cancer gene 1 and breast cancer gene 2 (BRCA 1 and BRCA 2, respectively) put you at higher risk for developing breast cancer.

You will likely need yearly mammograms before the age of 40. Ultrasound may also be recommended, depending on the density of your breast tissue.

Breast Density

Having dense breasts makes finding breast cancer more difficult and increases the risk of developing breast cancer.

Having a mammogram, ultrasound, and possibly an MRI can improve the accuracy of breast cancer screening for people with dense breasts.

Palpable Lump

There are times when an ultrasound is appropriate for breast cancer screening. When a palpable lump (one that can be felt by touch) exists but the mammogram is normal, ultrasound can be used to determine the likelihood of the lump being cancerous.

Insurance

Your insurance will usually cover breast ultrasound if your healthcare provider orders it to help diagnose a lump or a suspicious area seen on a mammogram. Most insurance companies won't cover breast ultrasound as part of routine cancer screening.

Other Breast Cancer Imaging Options

Neither mammograms nor breast ultrasounds will find all breast cancers. There are options for people who are at a high risk for breast cancer.

  • Breast magnetic resonance imaging (breast MRI) uses a powerful magnetic and radio waves to generate highly detailed images, especially of the soft tissue. Breast MRI might be best for young people with dense breasts who have significant risk factors for breast cancer.
  • Digital mammography uses less radiation than conventional mammograms.
  • 3D mammgoram: Also called digital breast tomosynthesis, this screening test may be able to spot more cancers in people with dense breasts. It may also result in fewer false positives.

Other tests may be used as investigational approaches to breast cancer screening, however, these are not standard recommended tests:

  • Elastography measures the stiffness of breast tissue.
  • Optical mammography without compression uses infrared light instead of X-ray.
  • Breast thermography can spot temperature variations suggestive of cancer, but it cannot be used as a substitute for mammography for early detection.

These techniques continue to evolve as researchers look for better ways to find breast cancer in the earliest stages of the disease.

Summary

There are some key differences between breast ultrasounds and mammograms that you should think about when you're trying to decide which option is best for you.

Mammograms remain the gold standard for screening, diagnosing, and following up after breast cancer. However, breast ultrasounds play an essential role in identifying breast cancer as well.

If a suspicious mass is discovered on a mammogram, a breast ultrasound can help further evaluate that area. People with dense breasts may need both mammograms and ultrasounds.

Unfortunately, neither mammograms nor ultrasounds are 100% accurate. Knowing how your breasts normally look and feel and reporting any changes to your provider is the first—and most important—step in early detection.

Frequently Asked Questions

  • Can a breast ultrasound detect cancer?

    A breast ultrasound can detect masses that look like they may be cancerous, but imaging is not enough to diagnose the disease. A biopsy, removal of a sample of tissue that is then examined in a lab, is required.

  • Can an ultrasound tell if a breast lump is noncancerous?

    A breast ultrasound can pick up fluid-filled masses, which are not likely to be cancerous. However, just as with solid lumps found on an ultrasound, a biopsy is needed to confirm the lump's status.

  • What does a breast ultrasound show that a mammogram doesn't?

    Breast ultrasounds can help identify lumps that can be felt but don't show up on a mammogram. Ultrasounds can also identify suspicious activity in dense breast tissue better than mammograms.

  • How do I prepare for a breast ultrasound?

    Avoid putting products like sunscreen, lotion, or powder on your chest the day of your ultrasound. Wear a two-piece outfit with a top that you can easily raise up or remove in case you're asked to put on a hospital gown.

13 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Madjar H. Role of breast ultrasound for the detection and differentiation of breast lesions. Breast Care. 2010;5(2):109-114. doi:10.1159/000297775

  2. Centers for Disease Control. What Is a Mammogram?

  3. Haghighi F, Naseh G, Mohammadifard M, Abdollahi N. Comparison of mammography and ultrasonography findings with pathology results in patients with breast cancer in Birjand, Iran. Electron Physician. 2017;9(10):5494-5498. doi:10.19082/5494

  4. National Cancer Institute. Mammograms.

  5. Miglioretti DL, Lange J, van den Broek JJ, et al. Radiation-induced breast cancer incidence and mortality from digital mammography screening: A modeling study. Ann Intern Med. 2016;164(4):205-214. doi:10.7326/M15-1241

  6. BreastCancer.Org. Mammograms.

  7. Mootz AR, Madhuranthakam AJ, Doğan B. Changing paradigms in breast cancer screening: Abbreviated breast MRI. Eur J Breast Health. 2019;15(1):1-6. doi:10.5152/ejbh.2018.4402

  8. Boca Bene I, Ciurea AI, Ciortea CA, Dudea SM. Pros and cons for automated breast ultrasound (Abus): A narrative review. J Pers Med. 2021;11(8). doi:10.3390/jpm11080703

  9. Ekpo EU, Alakhras M, Brennan P. Errors in mammography cannot be solved through technology alone. Asian Pac J Cancer Prev. 2018;19(2):291-301. doi:10.22034/APJCP.2018.19.2.291

  10. American Cancer Society. American Cancer Society Recommendations for the Early Detection of Breast Cancer.

  11. Brem RF, Lenihan MJ, Lieberman J, Torrente J. Screening breast ultrasound: past, present, and future. AJR Am J Roentgenol. 2015;204(2):234-40. doi:10.2214/AJR.13.12072

  12. Conant EF, Zuckerman SP, McDonald ES, et al. Five consecutive years of screening with digital breast tomosynthesis: outcomes by screening year and round. Radiology. 2020;295(2):285. doi:10.1148/radiol.2020191751

  13. Omranipour R, Kazemian A, Alipour S, et al. Comparison of the accuracy of thermography and mammography in the detection of breast cancer. Breast Care. 2016;11(4):260-264. doi:10.1159/000448347

Additional Reading
Headshot

By Serenity Mirabito RN, OCN
Mirabito is a certified oncology nurse. A commitment to patient advocacy informs her healthcare writing.

Originally written by Pam Stephan