Mammogram or Breast Ultrasound? Understanding Your Tests, Results and Next Steps

What Is a Mammogram?

A mammogram is a low-dose X-ray examination of the breasts. During the examination, each breast is gently compressed between two plates for a few seconds while images are taken.

Mammography is a recognised imaging technique used worldwide for breast cancer screening in asymptomatic women. It allows the radiologist to examine the breast as a whole and compare both breasts.

One of its particular strengths is its ability to detect tiny calcifications, some of which may be an early sign of breast cancer. Mammography can also identify masses, areas of asymmetry and subtle distortion of the normal breast architecture.

Modern mammography may be performed using standard digital mammography or digital breast tomosynthesis, also known as 3D mammography, which produces multiple thin images through the breast.

What Is a Breast Ultrasound?

Breast ultrasound uses high-frequency sound waves rather than X-rays to produce images of the breast.

During the examination, gel is placed on the skin and an ultrasound probe is moved over the breast. There is no radiation exposure, which means it can safely be done repeatedly when needed.

Ultrasound is particularly good at examining a specific area of concern. For example, if you can feel a lump, ultrasound can help determine whether it is a simple fluid-filled cyst or a solid mass. If it is solid, the radiologist can assess features such as its shape, margins and orientation to decide whether it appears benign or requires further investigation.

Ultrasound is also commonly used to examine an abnormality first seen on a mammogram and to guide procedures such as breast biopsies.

For women undergoing routine breast cancer screening, mammography remains the primary imaging examination. Ultrasound may sometimes be added, particularly in women with dense breasts or when there is a specific area requiring further assessment.

“My Breasts Are Dense. Should I Just Have an Ultrasound?”

This is an important question.

Breasts contain a mixture of fatty tissue and breast tissue. The amount varies in different individuals and with age. On a mammogram, fat appears relatively dark, while fibroglandular tissue appears white. Unfortunately, cancers also appear white. Thus, women with dense breasts are at risk of their cancers (if present) being masked by breast tissue.

In a radiology report, breast density is always mentioned. Breast density can be classified into four categories:

A: almost entirely fatty
B: scattered areas of fibroglandular density
C: heterogeneously dense
D: extremely dense

Categories C and D are considered dense breasts.

Dense breasts are common, especially in Asian women. Apart from reducing mammographic sensitivity, increased breast density is itself associated with increased breast cancer risk.

However, having dense breasts does not mean that you should skip your mammogram and have ultrasound instead.

Mammography can detect abnormalities and features of early breast cancer — particularly certain calcifications and architectural changes — that may not be visible on ultrasound. Depending on your breast density, age, personal risk factors and previous imaging, your doctor or radiologist may recommend additional ultrasound, MRI or another form of imaging.

There is no ‘one-size-fits-all’ approach — the decision is individualized.

“My Ultrasound Was Normal. Do I Still Need a Mammogram?”

Possibly, yes.

A normal ultrasound does not necessarily replace a mammogram when mammographic screening is indicated.

Some early breast cancers present mainly as tiny abnormal calcifications, which are much better assessed by mammography and may not be apparent on ultrasound at all.

This is why a woman who has had a reassuring ultrasound may still be advised to undergo a mammogram based on her age, symptoms or breast cancer risk.

“My Mammogram Was Normal, but I Can Still Feel a Lump. Should I Worry?”

A new or persistent breast lump should not simply be ignored because a mammogram was reported as normal.

When a woman has a palpable lump, the radiologist needs to make sure that the imaging findings correspond to the area she can actually feel. Targeted ultrasound is therefore commonly performed in addition to mammography.

For women aged 40 and above presenting with a palpable lump, diagnostic mammography followed in many cases by targeted ultrasound is commonly used. In younger women, ultrasound is often the first examination.

Importantly, imaging must always be interpreted together with the clinical findings. If a lump remains clinically concerning despite apparently reassuring imaging, further assessment — and occasionally biopsy — may still be necessary.

Screening Mammogram Versus Diagnostic Mammogram

These terms need some clarification.

A screening mammogram is performed in a woman without breast symptoms, with the aim of finding cancer before it becomes clinically apparent.

A diagnostic mammogram is performed in a woman with breast symptoms — for example, a new lump, nipple discharge, skin or nipple changes, or an abnormality found on a previous mammogram.

During a diagnostic examination, the radiologist may require additional specialised mammographic views and an ultrasound to properly evaluate the area.

Being asked to return for additional imaging after a screening mammogram therefore does not automatically mean that cancer has been found. It often means that more information is required before the radiologist can reach a final conclusion.

Understanding Your BI-RADS Result

Mammography, ultrasound and breast MRI reports commonly use a standardised system called BI-RADS — Breast Imaging Reporting and Data System.

The BI-RADS score helps the radiologist communicate the level of concern and inform the referring doctor what should happen next.

A BI-RADS 0 result is particularly worth understanding. It does not mean that you have cancer. It means that the assessment is not yet complete, and the radiologist needs additional mammographic views, ultrasound, previous images for comparison, or another investigation before giving a final category.

Similarly, BI-RADS 4 does not mean that you definitely have cancer. It means that the finding is sufficiently suspicious that tissue sampling is required to establish the diagnosis.

And even a BI-RADS 5 result remains an imaging assessment: the definitive diagnosis of breast cancer is generally made by examining tissue obtained during a biopsy.

Why Might I Need a Biopsy After My Scan?

Imaging is extremely useful, but imaging alone cannot always tell us exactly what a breast abnormality is.

If an area has suspicious features, the next step is usually an image-guided core needle biopsy. Small samples of tissue are removed and examined by a pathologist under a microscope.

This is an important distinction: a mammogram or ultrasound may tell us that something looks suspicious, but the biopsy establishes what the tissue actually is.

Many women who undergo breast biopsies may ultimately receive a benign result. Therefore a biopsy recommendation does not mean that cancer has already been diagnosed.

What About Breast Cancer Screening in Malaysia?

There is no population-based screening programme in Malaysia, as there is in Singapore, Japan, Taiwan and Western countries.

For average-risk women in Malaysia, the Ministry of Health Clinical Practice Guideline recommends that screening mammography may be performed every two years between the ages of 50 and 74. Women aged 40–49 may also consider screening after discussing the potential benefits and limitations together with their individual breast cancer risk. Women at increased or high risk may require an earlier and more intensive screening programme.

Malaysia's 2025–2035 national breast cancer downstaging roadmap also emphasises risk-based mammographic screening and improving access and adherence to breast screening.

Screening schedules differ between women, depending on factors such as: family history, known genetic mutations, previous breast cancer, previous high-risk breast lesions.

The Most Important Thing to Remember

Breast imaging is all about selecting the right examination — or combination of examinations — to determine the presence of breast cancer and other breast diseases.

For routine breast cancer screening, mammography is generally the foundation. For a new lump or an abnormality that needs closer evaluation or in the presence of dense breasts, ultrasound is often extremely valuable. In some women, particularly those at increased risk, breast MRI or other specialised techniques may also have an important role.

Unfortunately, no breast imaging test is perfect. It is the collective effort of the radiologist and surgeon, together with modern technology, that usually clinches the diagnosis.

If you notice a new lump, nipple inversion (nipple pulled inwards), spontaneous or bloody nipple discharge, persistent focal breast changes, skin dimpling or any other change that concerns you, seek medical assessment even if your most recent screening examination was normal. Do not delay.

The aim of breast imaging is not simply to perform more tests. It is to use the right test, for the right woman, at the right time, and to make sure that any finding is followed through appropriately.

This article provides general educational information and is not a substitute for individual medical assessment. Breast imaging recommendations should be based on your symptoms, age, breast density, previous imaging and personal breast cancer risk.