Breast Cancer Awareness Month: The Role of Ultrasound

As you can tell by the pink sneakers worn by NFL players, it’s Breast Cancer Awareness Month!

As such, over the course of the month, we will feature a few aspects of breast cancer diagnosis and treatment that may of interest to our readers. Today- the role of ultrasound in the diagnosis of breast cancer.

As we reported in June, former GMA host Joan Lundun was diagnosed with breast cancer. As she reported on her website, Joan Lunden’s Healthy Living:

“Two weeks ago I went for my annual mammogram as I do every year religiously, and thankfully it was all clear. That is always the moment where I feel I can breathe again. However for women who have dense fibrous breast tissue, as I do, often our doctors will recommend an ultrasound as well. My ultrasound that day revealed a tumor in my right breast.”

Everyone knows that mammography is important in the early diagnosis of breast cancer, but in this case, Joan’s mammogram was negative. Why did she have an ultrasound? What role should ultrasound play in the diagnosis of breast cancer and who should consider getting a breast ultrasound?

First, a little about breast anatomy:

The mature female breast is composed of essentially four structures: lobules or glands; milk ducts; fat and connective tissue. There are 15 to 20 sections (lobes) arranged in a spoke pattern, each lobe being made of many smaller sections (lobules). Lobules have groups of tiny glands that can make milk. After a baby is born, breast milk flows from the lobules through thin tubes (ducts) to the nipple. Fibrous tissue and fat fill the spaces between the lobules and ducts.

The glandular tissue is not uniformly distributed throughout the breast. There tends to be more glandular tissue in the upper outer portion of the breast. This is why many women complain of pain in this area just before their periods. It is also the site of about half of all breast cancers.

The consistency of the breast tissue varies from woman to woman, and even within the breasts of a single woman. The glandular portion has a firm, somewhat “nubby” feel to it, while the surrounding fat is typically soft. It is exactly this difference in the “feel” and density of these two tissues that allow them to be differentiated on a mammogram.

The breast tissue of younger women tends to be denser, with more glandular tissue and less fat. Over time, especially after the loss of estrogen that comes with menopause, the glandular tissue shrivels (involutes) and is replaced by fatty tissue.

There is some research that suggests that women with dense breasts have a higher incidence of breast cancer, although the reasons for this are unknown at the present time.
Dense breasts make it more difficult to detect breast cancer on a mammogram. This is because dense breast tissue can look white/gray on a mammogram- the same as cancer (see diagram below).

Photo credit: Susan B. Komen
Digital mammography- where the image is sent directly to a computer, rather than onto an x-ray film may be better for patients with dense breasts, as the images can be digitally altered to find hidden tumors.

Ultrasound is another method some physicians will use to supplement mammography in women with dense breasts. Ultrasound, or sonography, uses sound waves to look inside a part of the body. An instrument called a transducer is rubbed across the skin, which is lubricated with a special ultrasound gel. There is no radiation involved which is why it is safe to use in pregnant women.

Breast ultrasound is often used to evaluate breast problems that are found during a screening or diagnostic mammogram or on physical exam. Ultrasound can help distinguish between a cyst (fluid-filled sac) and a solid mass. Some physicians supplement the routine mammogram with an ultrasound in women with very dense breast tissue. Research has shown that it is not a good tool for mass screening for breast cancer, as there are an unacceptable rate of false negatives and positives.

The bottom line- ultrasound should not replace the mammogram for breast cancer screening. It may be used as an additional test to tell whether a mass seen on mammogram or felt by a physician is a cyst or solid mass, or as a supplemental test for women with particularly dense breasts.