Breast Ultrasound vs. Mammography: Which Is Best?

Though mammograms can miss tumors, they provide more information

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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 can also identify specific changes in the breast.

Since each test complements the other, healthcare providers may use both breast ultrasounds and 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
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Breast Ultrasound vs. Mammogram: Key Differences

The main differences between breast ultrasounds and mammograms are their roles in the breast cancer screening process. While each test is important in identifying possible cancer, they each have a different purpose.

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 the 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 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:

  • Unable to view the entire breast: Ultrasounds are conducted using a handheld transducer that slides across the skin to look for an abnormality. That means that the whole breast cannot be looked at closely.
  • Cannot examine deep breast tissue: An ultrasound helps providers see superficial lumps well, but a mammogram is better at looking for abnormalities that are deep in the breast tissue.
  • Does not evaluate the axillary lymph nodes (armpits): Evaluation of the axillary lymph nodes (divided into three levels: the lower, middle, and upper part of the armpit) can help determine if breast cancer has traveled beyond the breast. 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.

Should You Get a Breast Ultrasound or a Mammogram?

If you and your provider are trying to decide whether a breast ultrasound or a mammogram is the right choice for you, here are a few things to consider:

  • 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.
  • 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.
  • Age: People at average risk for breast cancer can begin yearly mammograms at the age of 40. At 55, mammograms can be spaced out in every other year.
  • 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.

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.
  • Elastography measures the stiffness of breast tissue.
  • Digital mammography uses less radiation than conventional mammograms.
  • Optical mammography without compression uses infrared light instead of X-ray.
  • Breast thermography can spot temperature variations suggestive of cancer but a 2016 study concluded that "thermography cannot substitute for mammography for the early diagnosis of breast cancer."

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.

12 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.
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Additional Reading

By Serenity Mirabito RN, OCN
Serenity Mirabito, MSN, RN, OCN, advocates for well-being, even in the midst of illness. She believes in arming her readers with the most current and trustworthy information leading to fully informed decision making.

Originally written by
Pam Stephan
Pam Stephan is a breast cancer survivor.
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