Mammogram or breast ultrasound: which test do I need?

These two tests are not rivals; they work together. A mammogram takes X-ray pictures of the breast and shows lumps, tiny calcium deposits and breast density ^[2]. Ultrasound uses sound waves and is very good for looking at one particular area, such as a lump ^{[1, 9]}. The table below shows the main job of each test.

The first test depends mostly on your age ^[1]:

• Under 30: ultrasound first. If the ultrasound is normal or shows a benign finding, usually no other test is needed. If it shows something suspicious, a mammogram and a biopsy are done.
• 30 to 39: ultrasound or mammogram; both are suitable. In a study of women this age with a lump or other symptom, ultrasound found almost all the cancers, while the mammogram found only about 6 in 10 ^[9].
• 40 or over: mammogram first (or a 3D mammogram). If something suspicious is seen, or if you had a normal mammogram in the past 6 months, an ultrasound is done as well.

In young women the breast tissue is usually denser and a mammogram helps less; that is why ultrasound comes first ^{[6, 9, 10]}.

A mammogram is an X-ray of the breast. The breast is placed between two plates that press it flat to get a clearer picture. Several pictures of each breast are taken from different angles ^[2].

• Screening mammogram: for a woman who has no symptoms.
• Diagnostic mammogram: when a lump or other change has been found, or a screening result was abnormal. More pictures are taken, from more angles ^[2].

The radiologist compares the new pictures with your earlier mammograms to look for changes, so bring your previous images and reports with you ^[2].

The pressure of the plates is uncomfortable for some women and painful for some; but most women do not find it painful, and the pressure for each picture usually lasts only a few seconds ^{[2, 11]}. These things help:

• Avoid booking the mammogram just before or during your period, when the breasts are more tender ^[2].
• If it hurts, tell the radiographer at once.
• If you are worried about pain, ask your doctor about taking a simple painkiller before the test ^[2].

Pressing the breast is needed: it spreads the breast tissue so that it does not overlap and the picture is clearer ^{[2, 11]}. If an earlier mammogram was painful for you, tell the imaging centre, and do not let it stop you from screening.

Yes; no test is perfect. In a large US study, screening mammograms found nearly 9 in 10 breast cancers ^[8]. Cancer is more likely to be missed in dense breasts, because both dense tissue and a tumour look white on the picture ^{[2, 10]}.

That is why two things matter:

• If you feel a lump or a change, see a doctor even if your last mammogram was normal; usually an ultrasound is done ^[1].
• Keep having mammograms on the schedule for your age ^[3]. Read more: At what age should you start having mammograms?

Dense breasts have more gland tissue than fat. This is common, it is not a disease, and density usually falls with age ^[10]. The mammogram report states your breast density; see what the letters A to D mean on the BI-RADS page.

Dense breasts have two effects: they raise the risk of breast cancer and they make the mammogram less accurate ^[10]. What does an extra test add?

• Extra ultrasound: in a large study in Japan of women aged 40 to 49, adding ultrasound to the mammogram found more cancers at an early stage and halved the cancers that show up between screening rounds; but it also gave more false alarms ^[6].
• Extra MRI: in a study in the Netherlands of women aged 50 to 75 with extremely dense breasts and a normal mammogram, an invitation to MRI halved the cancers that show up between rounds; but about 8 in 100 women who had the MRI got a false alarm ^[7].

It is not yet known whether these extra tests lower deaths from breast cancer, which is why recommendations differ ^{[3, 10]}. The American College of Radiology says an extra MRI or ultrasound can be considered in dense breasts ^[5]. If you have dense breasts, talk to your doctor about your own risk and whether an extra test makes sense.

Breast MRI finds cancers that a mammogram has missed, but it also gives more false alarms and is not needed by every woman ^{[4, 7]}. For most women at high risk, MRI is the best extra test ^[4].

A yearly MRI, along with a yearly mammogram, is recommended for these women ^[4]:

• carriers of a gene mutation, such as BRCA1 and BRCA2
• women whose doctor has calculated a high lifetime risk of breast cancer, usually based on family history
• women who had radiotherapy to the chest as a child or young adult
• women who had breast cancer before the age of 50, or who have had breast cancer and have dense breasts

In the first three groups, MRI usually starts at age 25 to 30 ^[4]. Every woman's breast cancer risk should also be assessed by age 25, so that women at high risk are found early ^[4]. Read more: Is cancer hereditary?

No; most women who are called back do not have cancer ^[2]. In a large US study, about 1 in 9 screening mammograms needed further checks, and fewer than 5 in 100 women who were called back had cancer ^[8]. Usually a few more mammogram pictures or an ultrasound of the same area are done ^{[1, 2]}. Read what the number at the end of the report means in What does BI-RADS 0 on a mammogram mean? If a biopsy is needed, see the next steps in How is cancer diagnosed?

Calcifications are tiny deposits of calcium in the breast tissue that show up as white spots on a mammogram ^[2].

• Larger calcifications (macrocalcifications): usually caused by ageing, an old injury or inflammation, and usually benign ^[2].
• Tiny calcifications (microcalcifications): when they are grouped in a certain shape or pattern, they may be a sign of very early cancer (ductal carcinoma in situ) or breast cancer ^[2].

For tiny calcifications, magnified mammogram pictures are usually taken, and if their shape looks suspicious, a biopsy ^[12]. Even when calcifications look suspicious enough to need a biopsy, in one study about 4 in 5 were not cancer ^[12].