Mammogram vs breast ultrasound

A mammogram compresses the breast between two plates and takes X-ray pictures from different angles. It is good at showing small clusters of calcium, distortion of tissue and masses, and it is the only imaging test proven to reduce deaths when used for screening in eligible age groups.

Ultrasound sends high-frequency sound through the breast and shows real-time pictures. It is good at showing whether a lump is a fluid-filled cyst or a solid mass, at examining a specific spot, and at guiding a needle. It does not reliably show the fine calcifications that mammography does, and a full-breast ultrasound is not used for population screening.

Dense tissue appears white on a mammogram, as do many cancers, so a cancer can be harder to see against the background. This is common in younger women and in some older women. Ultrasound shows density differently and can be better at examining a lump in dense tissue.

It is important to know that density is not an illness; it is a normal variation. But it explains why imaging choice varies between people, and why a clinician may add ultrasound when a mammogram is difficult to interpret.

In a symptomatic breast clinic, the standard is triple assessment: clinical examination, imaging and a biopsy where indicated. For women under about 35 with a lump, ultrasound is typically the first imaging test; for older women, mammography is generally combined with ultrasound. The reasoning is that imaging should match the tissue: sound waves for dense younger breasts, X-ray for fatty older ones, and both when a finding is unclear.

NICE guidance on suspected cancer (NG12) sets out when women should be referred urgently for breast assessment, including a new lump in women aged 30 and over. The imaging is then chosen by the breast team, not by the patient's preference for one test.

• Aged 50 to 71 and invited by the NHS programme: attend the mammogram you are invited to.

• A new breast lump at any age: see a GP promptly for assessment and possible urgent referral rather than choosing a scan yourself.

• Pregnant or breastfeeding with a lump: ultrasound is usually the first test.

• A mammogram report says tissue is dense and you have a high family risk: ask the breast team whether MRI or ultrasound would add value in your case.

• Pain without a lump: clinical review first; imaging is chosen by symptoms and age.

Ultrasound is not a "safer mammogram" that can replace screening. It finds different things and is less standardised. And a mammogram is not harmful in the sense people often fear; the dose is low, though it is still used where benefit is expected.

It is also not true that a normal mammogram means any lump can be ignored. A palpable lump needs assessment regardless of an earlier normal result.

• Which scan is appropriate for my age and symptoms, and why?

• Does my breast density change what you recommend?

• If something is seen, will I have a biopsy and how quickly will I get results?

• How often should I be screened given my family history?