How Dense Breast Tissue Can Increase Your Breast Cancer Risk

Once you have your first mammogram, or if you’ve already had one, knowing whether you have dense breast tissue is important for understanding your breast cancer risk. The denser your breast tissue is, the trickier it can be for doctors to spot small problem areas in your breasts. Radiologist Dr. Roberto Fragomeni, UnityPoint Health, explains everything women need to know about dense breast tissue and what it means for your risk of developing breast cancer.

What is Breast Dense Tissue and What Causes It?

The breast is made of a mixture of different glands and tissue, including:

• Fatty tissue
• Milk gland tissue
• Milk ducts
• Fibrous tissue (bands that keep the glands and fatty tissue together)

Breasts are considered dense if you have a lot of glandular tissue, which consists of milk gland tissue, milk ducts and fibrous breast — but not a lot of fatty breast tissue.

“If a woman has greater glandular tissue and less fatty tissue, they’ll have dense breasts, which is just a phrase that helps us classify how much fat and glandular tissue there is for a person,” Dr. Fragomeni says.

“So, the more glands and/or fibrous tissue you have, the denser the breast,” he adds.

Should I Be Worried about Dense Breast Tissue?

While dense breasts alone are not cause for alarm, there’s a higher risk associated with breast cancer. Staying on top of your mammogram schedule and knowing if you have dense breast tissue is key. However, dense breast tissue isn’t something you can control or that needs to be treated, but it can change on its own over time. Women have different variations of the amount of fat and glandular tissue in their breasts. Dense breast tissue also changes depending on your age, genetics, hormones and weight.

• Age: Younger women tend to have denser breasts than older women but not always.
• Genetics: Dense breast tissue is typically inherited. If your mother had dense breasts, you’re more likely to have dense breasts as well.
• Hormones: As women age and enter menopause, they lose some of the glandular tissue (breast density) and fatty tissue increases. This doesn't happen to everybody, but it’s common. Hormone replacement therapies and birth control pills that have estrogen can make breasts look denser as well as when you’re pregnant or lactating.
• Weight: People who have a lower percentage of body fat tend to have dense breasts, too, as fatty tissue decreases with weight loss and exercise. If you gain weight, you gain fatty tissue, and the breast can become less dense.

What Does Dense Breast Tissue Feel Like?

Dense breast tissue isn’t something you or your doctor can feel, and you can’t see it on physical examination either. A radiologist has to look at a mammogram to see if you have dense breasts and what category they fall into.

How Can You Tell Apart Dense Breast Tissue from a Lump?

Lumpy breasts are also different than dense breasts. Dr. Fragomeni says some women can have both.

“However, if you do feel a lump, always chat with your doctor. They can help determine if you need imaging,” he says.

The Four Categories of Dense Breast Tissue

Dense breast tissue is typically classified into four categories based on the proportion of dense tissue in the breast as seen on a mammogram. There categories include:

• (A) Almost Entirely Fatty: Breasts are mostly fatty and have the least amount of glandular and/or fibrous tissue. They’re considered non-dense.
• (B) Scattered Fibroglandular Density: Fibrous and/or glandular tissue is present in the breast, but it’s not considered dense. There’s still a lot of fatty tissue.
• (C) Heterogeneously Dense: Glandular tissue takes up more space than fatty tissue in the breast.
• (D) Extremely Dense: There’s very little fatty tissue in the breast. Mostly glands and fibrous tissue hold the breast together.

“Most women fall into the middle two categories, which is scattered areas of density or heterogeneously dense breasts, or B and C. So, 40% are in category B and 40% are in category C. Then, 10% have almost entirely fatty tissue, and the other 10% have extremely dense breasts,” Dr. Fragomeni says.

If you can’t remember which category you fall into, check with your doctor. Dr. Fragomeni assures that radiologists always comment on a woman’s breast density on mammogram reports, as it’s regulated by Congress. 

Can Dense Breast Tissue Turn into Cancer?

Dense breasts have an increased risk of developing into cancer. This is thought to be caused by the make-up of dense breast tissue and cancer hiding under the tissue, making it harder to see on a mammogram.

“If you compare a person with mostly fatty breasts with someone who has extremely dense breasts, the person with extremely dense breasts has four to six times higher risk of developing breast cancer than the patient with the fattier breast,” Dr. Fragomeni says.

Your breast density has a higher impact on your cancer risk than when you went into menopause and/or had children.

“Breast cancer is also harder to see on a mammogram when someone has dense breast tissue. It can hide under the glandular tissue,” he says.

What’s the Best Imaging for Dense Breast Tissue?

Mammograms are appropriate for dense and non-dense breasts. It’s the only imaging modality that’s been shown to reduce deaths from breast cancer. Dr. Fragomeni says 3D mammography is best.

Is Ultrasound or MRI Better for Dense Breasts?

“Nothing replaces the mammogram, but ultrasounds and/or breast MRIs are appropriate, in addition to the mammogram, for people who are considered high risk. That means you have a family history or other high-risk factors,” he says.

If you have dense breasts and additional risk factors, Dr. Fragomeni says the best imaging to add to your routine mammogram screenings is the breast MRI. It has the highest sensitivity and ability to find cancer.

“One of the drawbacks is it can find things that aren’t cancer as well, so not everybody should use it all the time,” he says. This can lead to additional biopsies.

Another supplemental screening option is the ultrasound. It’s best for patients who aren’t high-risk or those who can’t get a breast MRI, because they have allergies to iodine, metal in their bodies or are claustrophobic.

Dr. Fragomeni says patients who fall into a dense breast category should talk to their doctors about supplemental screening, such as a breast MRI or ultrasound, and to find out what is covered by insurance.

Does Dense Breast Tissue Cause Pain?

No, dense breast tissue doesn’t hurt. If you have dense breasts, you can have breast pain the same way a person without dense breasts can. Most commonly, reasons for breast pain include:

• Hormones or a menstrual cycle. Breast pain is on the side of the breast and reaches the armpit.
• Cysts, non-cancerous growths or inflamed lymph nodes that aren’t cancerous can cause tender breasts.

Issues not related to the breast can also cause breast pain, including:

• Shingles
• Musculoskeletal pain
• Inflammation in the chest wall

What Does it Mean if You Have Dense Breast Calcifications?

Dr. Fragomeni says dense breasts and calcifications are two different things. Patients can have calcifications, which are deposits of calcium, whether they have dense or non-dense breasts. They tend to be non-cancer related and look like a grain of salt scattered on a mammogram. They’re common after the age of 50.

When they may indicate cancer is when a radiologist sees they’re increasing or grouping into certain shapes that suggest there’s cancer, or something higher risk, forming.