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Breast (Chest) Density Fact Sheet

What is breast (chest) density?

All breasts are made up of fibroglandular (fi-bro-gland-you-lur) and fatty tissue. Fibroglandular tissue, which is also known as dense tissue, keeps the breasts in place and helps make and carry milk to the nipple. Fatty tissue is fat that gives shape to the breasts.

Some people have more dense tissue than others. Breast (chest) density is a measure of how much dense tissue a person has in their breasts.

Are there different types of breast (chest) density?

Yes. There are 4 types of breast (chest) density.

  • Type A, which means the breasts are almost entirely made up of fatty tissue.
  • Type B, which means the breasts are mainly made up of fatty tissue, with some small areas of fibroglandular (dense) tissue.
  • Type C, which means the breasts have a mix of fatty and fibroglandular (dense) tissue.
  • Type D, which means the breasts are almost entirely made up of fibroglandular (dense) tissue.

People with density type A have the lowest density, while people with density type D have the highest density.

Can my breast (chest) density change?

Yes. Breast (chest) density may not stay the same throughout someone’s life. People may have lower density as they age. Some people have higher density after taking estrogen.

How can I know what my breast (chest) density is?

The letter that came with this fact sheet tells you your breast (chest) density. Your density is based on your mammogram, which is an X-ray of your breasts. On a mammogram, fibroglandular (dense) tissue looks white, while fatty tissue looks grey or black. Having a mammogram is the only way to know your density. You cannot tell what your density is based on the way your breasts look or feel.

Why is it important to know what my breast (chest) density is?

There are 2 reasons why it is important to know your breast (chest) density:

  • Having higher density can make it hard for doctors to see breast cancer on a mammogram because fibroglandular (dense) tissue looks the same as breast cancer on a mammogram.
  • People with higher density have a higher chance of getting breast cancer than people with lower density. The reasons for this are not well known.

What should I do if I have type A, B or C breast (chest) density?

If you are age 50 to 74 and have type A, B or C breast (chest) density, your next mammogram could be in 1 year or 2 years. Please check the letter that came with this fact sheet to find out when you should have your next mammogram. If you are over age 74, talk with a doctor or nurse practitioner to decide whether you should get mammograms in the future. Be sure to tell a doctor or nurse practitioner if you notice any changes in your breasts.

Does having type D breast (chest) density mean I have breast cancer?

No. Having type D breast (chest) density does not mean you have breast cancer. It also does not mean that you will get breast cancer in the future. It only means that you have a higher chance of getting breast cancer than someone with lower density.

What should I do if I have type D breast (chest) density?

If you are age 50 to 74 and have type D breast (chest) density, you should get a mammogram every year. Type D density can make it hard for doctors to see breast cancer on a mammogram because fibroglandular (dense) tissue looks the same as breast cancer on a mammogram. Having a mammogram every year can help doctors find changes in the breast sooner and treat them if needed. Talk with your doctor or nurse practitioner to find out if you need more imaging tests.

Breast density may not stay the same throughout someone’s life. If your density becomes lower and there are no other reasons for you to have mammograms every year, you will be invited to get a mammogram every 2 years. If you are over age 74, talk with a doctor or nurse practitioner to decide whether you should get mammograms in the future.

Be sure to tell a doctor or nurse practitioner if you notice any changes in your breasts.

Why is the word “chest” sometimes used when describing the breasts?

Some people, including trans men, transmasculine people and nonbinary people, may prefer the term “chest.” The term “breast” is still used to make sure this letter is clear for everyone.

How can I contact the Ontario Breast Screening Program (OBSP)?

Visit cancercareontario.ca/obsp, call us toll-free at 1.866.662.9233 from Monday to Friday, 8:30 a.m. to 5:00 p.m., or email us at cancerinfo@ontariohealth.ca.


Need this information in an accessible format?
1.877.280.8538 / TTY 1.800.855.0511 | info@ontariohealth.ca.

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