Dense breast tissue can cloud diagnostic images

When a woman has a mammogram performed, she may receive a letter telling her that she has dense breast tissue. Having dense breast tissue can make it harder to read a mammogram, and it may be connected to a higher risk of developing breast cancer.

Women’s breasts consist of fat, fibrous tissues, milk glands and milk ducts. Having dense breast tissue means that a woman has less fat tissue and more fibrous tissue.

“Breasts are made up of a mixture of fatty and glandular tissue, blood vessels and things like that,” Dr. Hugh Holloway, a diagnostic radiologist with Radiology Associated of Dothan, said. “In different ladies, it comes in different degrees of fatty and fibrous tissue, which affects our ability to interpret those (mammogram) and, to some degree, affects the lady’s breast cancer risk.”

Radiologists now alert women, in layman terms, the results of their mammograms, thanks to a federal mandate called the Mammogram Quality Standards Act (MQSA), according to Holloway.

“Each facility shall send each patient a summary of the mammography report written in lay terms within 30 days of the mammographic examination,” the act states on the U.S. Food and Drug Association’s website. “If assessments are ‘suspicious’ or ‘highly suggestive of malignancy,’ the facility shall make reasonable attempts to ensure that the results are communicated to the patient as soon as possible.”

If a woman has dense breasts, that information is also noted with the results of her mammogram. In Alabama, legislation also requires that patients with dense breast tissue be notified of the risk factors associated with it.

The message patients receive is similar to this message, cited in the Alabama Code of Law:

“Your mammogram shows that your breast tissue is dense. Dense breast tissue is very common and is not abnormal. However, dense breast tissue may make it harder to find cancer on a mammogram and may also be associated with an increased risk of breast cancer. This information about the result of your mammogram is given to you to raise your awareness. Use this information to talk to your doctor about your own risks for breast cancer. At that time, ask your doctor if more screening tests might be useful, based on your risk. A report of your results was sent to your physician.”

Alabama was the 19th state to pass this type of legislation, according to Holloway.

When reading a mammogram, the density of a woman’s breasts is measured using BI-RADS (Breast Imaging Reporting and Data System).

Holloway said there are four categories under the BI-RADS system used to measure breast density. These categories are predominately fatty, scattered fibroglandular, heterogeneously dense and extremely dense.

When studying a mammogram, Holloway said predominately fatty breasts are “quite dark,” meaning there is little fibrous tissue seen in the image.

Images of breasts in the scattered fibroglandular category, with “0-25 percent dense tissue” show scattered fibrous tissue. This tissue is usually white in the image.

Images of heterogeneously dense breasts, according to Holloway, have “progressively white” shading throughout the breast.

“Between 25-75 percent (of the breast) is occupied by this more dense tissue,” he said.

Finally, images that show extremely dense breasts are almost completely shaded in white with the fibrous tissue.

“The net effect of this density is that it could obscure a tiny breast cancer, which could be a tiny soft tissue density or it could be a cluster of calcifications,” Holloway said. “That was one impact of the dense breast: it makes the mammogram more difficult to interpret because it can hide things.”

Dr. Sam Sawyer, with Sawyer Surgery Clinic, said dense breast tissue often occurs in younger women who are not of the age to begin having mammograms.

“Dense breast tissue is young breasts, young ladies under the age of 40 “ Sawyer said. “Their tissue is dense because they still have functioning breast tissue. As a woman gets older and she doesn’t have hormones anymore, then the breast tissue thins out and the breasts are mostly fatty tissue.

“On a mammogram, you can see a 1 mm spot in a woman who’s 80 years old. You never see that in a 40 year old because of the density.”

Sawyer said because mammograms are not often performed on women younger than 40, self-exams or exams performed by their regular physicians are important to detect any anomalies in the breast.

“It’s more than dense breasts,” he said. “It’s the younger people, and they’re not even going to do mammograms on young people. If a 20-30 year old came in with a lump in their breast, I wouldn’t do a mammogram on them. I wouldn’t see anything (because of their breast density).

Sawyer said it women should “know their breasts like they know their way back home.”

“It’s important that you know what your breasts feel like so that if something new pops up, you’ll recognized it... rather than not know if some density has been there all along,” he said. “It’s also important, if you find something, to come get it checked out either with your primary care or with a breast surgeon.

“If (the doctor) says, ‘It’s just dense breast tissue,’ don’t be embarrassed that you wasted somebody’s time. You didn’t. You felt it, you didn’t know what it was and now you do.”

When a younger woman with dense breasts performs a self-exam, Sawyer said she might not understand when a lump is normal or when it is not.

“The thing is, I tell women (who have dense breasts) that cancer feels like a brick in a cobblestone street,” Sawyer said. “It’s different. It’s going to stand out.

“It’s sort of what I do is be able to discern whether this is just more breast tissue or if it is something worrisome. I can usually tell by feeling it, but we can confirm it, almost always, with an ultrasound.”

He also said that feeling a lump in a younger, denser breast does not mean that the lump will be as small as one that is detected on a mammogram of an older woman.

“If it’s big enough to be palpable, yeah, it’s bigger,” he said. “We don’t have a really great screening test for young people who have dense breasts.”

Holloway echoed that women typically have less dense breast as they get older in most cases.

“Number one is your age,” he said. “As you get older, breast density goes down. The second thing is you’ve been pregnant and, even if you didn’t breast feed, your breasts will become dense. Then, it should go down after the pregnancy.”

He also said medications, such as hormones or hormone blockers, could also affect the density of breast tissue; however, just having dense breast tissue can increase a woman’s risk for developing breast cancer.

“There’s an increased recognition that just having (dense breast tissue) is a statistical risk factor for breast cancer,” Holloway said, stating he has read research that states women with dense breast tissue could have 5xs the risk of developing breast cancer.

The Mayo Clinic also states that having dense breast tissue can increase a woman’s risk for breast cancer, but “doctor’s aren’t certain why.”

In general, women should be aware if they have dense breast tissue and follow the instructions on determining if any abnormalities in a mammogram or other screening tests are cancerous or not.

“For the average lady having a mammogram, it’s a screening test, so we do the mammogram; we look at that to see if there’s anything suspicious,” Holloway said. “If we see something suspicious, we call her back for additional studies, which might be more mammograms, or it might be a breast ultrasound.

“In general, what’s done in Enterprise is, you have a screening mammogram from age 40 on. If something is seen, then you’re called back then for a diagnostic mammogram,” he said.

Holloway said there are other types of imaging tests used for certain women with “high risk” factors, including breast MRIs.

Sawyer also said 3D mammograms could be an important tool to use in screening and diagnostic testing.

“It’s probably most valuable in ladies with dense breasts,” he said. “It really doesn’t find a whole lot more cancers,” but it does help stop some women from having to have unnecessary biopsies performed.

Though dense breast tissue may make a mammogram harder to read, Holloway said it was important to still have them performed regularly. He knows this personally.

“My mother had breast cancer; I lost a sister-in-law to breast cancer at age 54, so I strongly believe in it,” he said.