Mammography or Ultrasound? Understanding Breast Cancer Screening Options — With International Perspectives

6月 29, 2025admin Breast check

In Japan, biennial (every two years) mammography screening is recommended for women aged 40 and above. However, some people are advised to undergo ultrasound (breast echo) screening instead due to having “dense breast tissue” as identified during a check-up. Others may wonder, “Is there a less painful alternative to mammography?”

At our clinic, we often receive questions such as:
“Which should I choose—mammography or ultrasound?”

Both methods are valuable tools for the early detection of breast cancer, though each has its own strengths and limitations. Understanding the differences between mammography and ultrasound can help you make an informed decision.

Mammography vs. Ultrasound: A Comparison

Feature	Mammography	Ultrasound (Breast Echo)
Method	Uses X-rays to image the breast	Uses high-frequency sound waves to examine inside the breast
Pain	May cause discomfort or pain due to breast compression	Almost painless
Strengths	Detects microcalcifications and structural distortions in breast tissue	Good at detecting small lumps in dense breasts and observing changes in milk ducts
Limitations	May miss cancers hidden in dense breast tissue	Poor at detecting calcifications
Radiation Exposure	Yes	None

Mammography is the most commonly used screening tool worldwide for breast cancer. By compressing the breast tissue during the scan, radiation exposure is minimized while producing clearer images. It is especially effective in detecting small, non-palpable lumps or microcalcifications.

That said, for women with dense breast tissue—common in Japanese women (about 40–50%)—mammography can be less effective as dense tissue can obscure tumors. These individuals may benefit from supplemental ultrasound screening.

Radiation from mammography is a common concern. However, the dose is comparable to the radiation you receive from a round-trip flight between Japan and the U.S., and the risk is considered low compared to the benefit of early cancer detection.

Breast Ultrasound (Echo)

Ultrasound is a non-invasive, radiation-free, and relatively comfortable method for screening, especially effective for women with dense breast tissue. While its effectiveness as a stand-alone screening tool is still under study, combining it with mammography has been shown to improve cancer detection rates.

However, ultrasound accuracy can vary depending on the skill of the technician or physician. It also tends to lead to more follow-up (diagnostic) tests, which may cause additional stress and cost.

For women with larger breasts, mammography can more easily capture the full view, whereas ultrasound may not penetrate deeply enough to visualize all areas.

During pregnancy, when breast tissue tends to be denser and radiation should be avoided, ultrasound is the preferred screening method. If mammography is deemed necessary, protective measures are taken to ensure safety.

For individuals with silicone breast implants, mammography is generally not recommended at our clinic due to the potential risk of implant damage from compression. If necessary, a modified technique is used to visualize the breast tissue without damaging the implant.

Which Test Should You Choose?

The right test depends on your age, breast density, and personal risk level for breast cancer.

① Women Aged 40 and Above

Mammography is the gold standard for breast cancer screening in this age group, as it has been proven to reduce breast cancer mortality through early detection. However, if you have dense breasts, adding an ultrasound may improve the accuracy of your screening.
At our clinic, we recommend combining mammography with ultrasound for comprehensive screening.

② Women Under 40

Younger women tend to have denser breast tissue, which reduces mammography’s sensitivity. Additionally, due to concerns about radiation exposure in this age group, we recommend starting with ultrasound and adding mammography only if needed.

③ Individuals at High Risk (Regardless of Age)

If you have a family history of breast cancer or a known genetic predisposition, combining both mammography and ultrasound can significantly enhance early detection.
For those seeking thorough screening or who have dense breasts, both tests are recommended for a more complete evaluation.

Breast Cancer Screening Guidelines: International Overview

United States (USPSTF): Mammography every 2 years starting at age 40 (updated from 50 in recent years), with some organizations recommending annual screening.
United Kingdom (NHS): Mammography every 3 years for women aged 50 to 71. Women under 50 are not routinely screened unless they are at high risk.
Canada: Varies by province, but generally mammography is recommended every 2–3 years starting at age 50, with some areas starting at 40.
Australia: Mammography every 2 years for women aged 50 to 74. Women aged 40–49 or over 74 can choose to be screened after consulting with their doctor.
South Korea: Mammography every 2 years for women aged 40 and over, similar to Japan.

Japan’s guidelines are in line with international standards, but individual risk factors should always be taken into account.

Understanding the Pros and Cons of Screening

The greatest benefit of breast cancer screening is early detection, which expands treatment options and improves the chances of cure.

However, no screening method is 100% perfect. Additional considerations include:

✔ Screening can be costly and time-consuming
✔ Waiting for results can cause anxiety
✔ Mammography may be painful and involves radiation
✔ Ultrasound accuracy depends on examiner skill
✔ False positives can lead to unnecessary tests

Knowing these advantages and limitations allows you to choose the method that best suits your needs.

In Summary: It’s Not “Either/Or,” but Using Both Appropriately

Mammography and ultrasound are complementary, not competing tests.

Rather than asking “Which is better?” it’s more useful to ask,
“Which combination is right for me, based on my age, breast density, and risk?”

The best approach is to discuss your screening plan with a healthcare provider, considering your personal circumstances. And remember, undergoing screening is just one step. Being aware of your own breast condition and seeking medical attention if any changes occur is equally important.

Please feel free to consult with us anytime about any concerns or questions related to your breast health.