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When used alongside mammography, breast ultrasound can help provide a more accurate diagnosis of breast cancer. Find out how and why.

Breast ultrasound or mammography: what are the main differences?

Although breast cancer is not among the most lethal cancers, it has a high mortality rate, particularly among women. However, the earlier it is detected, the greater the chances of successful treatment.

Figures from Portugal’s National Breast Cancer Screening Programme clearly demonstrate the importance of early detection.

By the end of 2022, according to the Portuguese League Against Cancer, more than 5.3 million screening mammograms had been performed and more than 30,000 women had been referred for diagnosis and treatment.

This has enabled less aggressive and more effective treatment and, in many cases, complete recovery.

Mammography is the imaging examination used to screen for breast cancer. However, in some cases, complementary examinations such as breast ultrasound are also required.

In this article, you can learn about the differences between breast ultrasound and mammography, when each examination is recommended and when both may be necessary.¹ ² ³

Differences between mammography and breast ultrasound

A mammogram may be performed in people experiencing pain, lumps, nipple discharge or other signs or symptoms of breast cancer. It is a specific examination used for screening and diagnosis.² ⁴

A breast ultrasound, on the other hand, is a complementary examination to mammography. It can help determine whether a lump is a fluid-filled cyst, which is usually non-cancerous, or a solid mass, which may be cancerous.

When is a mammogram recommended?

For breast cancer screening, according to the guidelines of the Portuguese Directorate-General of Health, mammograms should be performed every two years between the ages of 50 and 69 in asymptomatic individuals.

As this examination uses only a small amount of radiation, having it every two years is considered safe.

However, it may be recommended earlier, even before the age of 35, depending on symptoms and risk factors.

Since between 5% and 10% of diagnosed cancers have hereditary or genetic characteristics, breast cancer screening should be performed annually when a person has:⁵

A family history of breast or ovarian cancer;
Inherited genetic mutations.

This criterion applies not only to women but also to men, as men can also develop breast cancer, although it is more common in women.

Other factors may also require annual mammography, including:

A personal history of breast cancer;
Certain benign breast conditions (non-cancerous), such as atypical ductal hyperplasia and/or lobular neoplasia;
Dense breast tissue.

Types of mammograms

There are two main types of mammography:⁵ ⁶

2D digital mammography: both digital and conventional mammography use X-rays to produce an image, but digital mammography provides an electronic image stored as a computer file. This digital mammography is bilateral, meaning that images are taken from different angles.
3D digital mammography: this bilateral mammography allows images to be viewed in three dimensions, providing healthcare professionals with greater clarity when examining breast tissue.

What is a breast ultrasound used for?

Breast ultrasound cannot detect cancer on its own. It is a complementary imaging examination used to evaluate a specific area of the breast that appears unusual, unclear or different from the rest of the breast on a mammogram.

This examination may also be recommended if the person:⁷

Is under 25 years of age;
Has particularly dense breast tissue: a mammogram may not be able to produce sufficiently clear images through dense tissue;
Is pregnant: when comparing breast ultrasound and mammography, ultrasound is safer for the foetus because it does not use radiation.

Breast ultrasound or mammography?

Breast ultrasound creates images using sound waves, which means the person is not exposed to radiation. However, the examination has limitations and is usually used to assess a specific area of the breast.

Mammography is the preferred medical imaging technique for examining and analysing the entire breast.

However, for people at high risk of breast cancer, combining both examinations may be recommended.²

What happens if the examinations detect abnormalities?

An abnormal mammogram result does not necessarily mean cancer.

If the results are not fully conclusive, breast ultrasound may complement the diagnosis.

Depending on the findings shown by the ultrasound, it may also be necessary to perform a magnetic resonance imaging (MRI) scan or a biopsy.⁴

If cancer is diagnosed, the doctor will plan the most appropriate treatment.

All women diagnosed with breast cancer will undergo hormone receptor testing. This information is important to determine whether the cancer requires oestrogen or progesterone to grow.

The results of this test may influence the choice and planning of treatment.⁵ ⁹

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