What exactly is an ultrasound? How does it work? And why does my doctor want me to have one? Everything you need to know about breast ultrasound: the what, how, and why of this common screening device.
Q. I went for my regular mammogram, and I got a callback for another view. Now they want to do an ultrasound. What does that mean? I’m scared…
A. First of all, it’s natural to be scared when everything doesn’t go as usual with your annual mammogram. About 10% to 15% of all screening mammograms result in a “callback” – the need for a further mammogram. And about 95% of callbacks end right there, with no further screening necessary. The radiologist might have seen a piece of breast tissue folded over on itself, regular glandular tissue viewed from an odd angle, or something else that, with another, different mammogram, looks just fine.
But sometimes, even after a second view, something doesn’t look quite right. At that point, the radiologist may order an ultrasound, a.k.a. sonogram.
Q. So, is the ultrasound likely to show something serious? Does this mean I have cancer?
A. No, not at all. The vast majority of breast lumps, or “abnormalities” seen on mammograms, are NOT cancer. Even if the ultrasound were to prove inconclusive and you needed a biopsy, about 85% of biopsies are negative; no cancer. So odds are your ultrasound will show that what the radiologist saw is NOT cancer.
Q. What kinds of things can an ultrasound show?
A. The ultrasound’s main advantage over mammograms is that it’s very good at showing whether a lump or mass is solid, or filled with fluid. A solid lump needs further examination, either via MRI, or biopsy. But if the lump is filled with fluid, your testing is done: the lump is a cyst.
Cysts (and accompanying fibrocystic change) are quite prevalent in women under the age of 50. In fact, the most common cause of non-cancerous breast lumps in women between the ages of 30 and 50 is cysts. On an ultrasound, a cyst is dark black outlined in white; it’s very distinctive, and easily identified.
An ultrasound might also show a plugged milk duct, or a fat lobule, other conditions mammograms are unable to distinguish from regular breast tissue.
Q. Well, I feel better knowing that I’m more likely to have a cyst than cancer. I’m still worried, though. What’s the test like?
A. An ultrasound can take 20 to 30 minutes, but it’s an easy test. You’ll lie on a table with your arm above your head, and the person performing the ultrasound (the sonographer) will rub a clear, water-based gel on your breast; sometimes it feels uncomfortably cold for a minute, but it warms up fast.
The sonographer will run a small device, called a transducer, over the area of your breast with the lump. The gel helps the transducer maintain contact with your skin. The transducer sends images to a computer screen, which the sonographer watches as s/he works. Since this is all done in real time, s/he can easily adjust the area being scanned to view the lump from different angles.
Unlike radiation-based mammograms, an ultrasound uses high-frequency sound waves to “see” tissue in the breast. These sound waves bounce back at different rates, depending on what they strike; and a computer interprets the information and turns it into a visual image.
Sometimes the sonographer or doctor will want to review the images, and you may be asked to wait. Other times, it’s clear right away that what you have is a cyst; and at the end of the exam you can simply wipe the gel off, get dressed, and go home. You shouldn’t experience any after-effects at all, and can go back to your usual activities right away.
Q. And what happens after the ultrasound? Do I need to do anything else?
A. If it’s determined you have a cyst, then there’s no need for any follow-up, unless the cyst is particularly large and painful – in which case your doctor may choose to drain it.
If the ultrasound shows that the lump or mass is solid, then the screening process will continue – either with an MRI, which is more sensitive than mammography and can show a more complete, detailed image of any solid mass; or with a biopsy.
Q. I have a friend who says she has “dense breasts,” and she says she always gets an ultrasound along with her mammogram, because it’s more accurate. Is that true? Should I ask for an ultrasound every time I have a mammogram?
A. Dense breasts are a clinical condition that need to be assessed by your doctor or radiologist. The term refers to breasts that have very little fat, compared to glands and connective tissue. And, while fat shows up clear on an X-ray (mammogram), other tissue – including tumors – shows up opaque. Thus it’s much easier for tumors to “hide” in dense breasts than in normal breasts.
So, can women with dense breasts skip the mammogram, and just rely on ultrasound for their regular screening? No, because ultrasound can’t pick up the tiniest tumors or pre-cancerous microcalcifications that a mammogram can spot. The best choice for these women is a mammogram combined with ultrasound, which is about 50% more effective at spotting possible tumors in dense breasts than a mammogram alone.
Since women with dense breasts also have a very slightly increased risk of breast cancer, your friend’s doctor is being proactive in selecting the best combination of screening processes possible for her. Women with normal breasts derive no extra benefit from the ultrasound/mammogram combination, compared to mammogram alone; so you wouldn’t need an ultrasound along with your annual mammogram.