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Breast Density

Specialising in Women's Health

Dense breast tissue is an important point to mention, because it is a normal and common breast condition in especially younger women before the menopause, who are not included in any breast health screening program.

What is dense breast tissue?

Dense breast tissue refers to the appearance of breast tissue on a mammogram.

It's a normal and common finding.

Breast tissue is composed of milk glands, milk ducts and supportive tissue (dense breast tissue), and fatty tissue (non-dense breast tissue). When viewed on a mammogram, women with dense breasts have more supportive tissue than fatty tissue.

On a mammogram, non-dense breast tissue appears dark and transparent.

Dense breast tissue appears as a solid white area on a mammogram, like cotton wool, which makes it difficult to see through and find tiny tumours, which are calcifications and are also white.

​Doctors know dense breast tissue makes breast cancer screening with mammography more difficult and mammography may in itself increase the risk of developing breast cancer.

Breast density is usually detected on a mammogram, which is only offered to women for free between the ages of 50 and 70 in the UK. However, far more younger women are now diagnosed with breast cancer and are missing out on an opportunity to an early detection, because of this lack of service.

But even if an NHS mammography screening was offered, possibly due to the low accuracy in detecting small tumours in this age group, the tumour would have been missed anyway.

Thermography on the other hand is not subjected to needing to look inside the breasts: hormone and tumour activity is reflected in the skin surface, whether or not an activity is deep in the breasts or just under the surface.

This gives thermography a big advantage as a first line breast health check over mammography with the additional bonus of no radiation.

How is dense breast tissue determined?

There are 4 levels of density. The radiologist who analyses your mammogram determines the ratio of non-dense tissue to dense tissue and assigns a level of breast density.

Levels of density are described using results reporting system called BI-RADS.

The levels of density are:

  • Almost entirely fatty indicates that the breasts are almost entirely composed of fat. About 1 in 10 women have this result.

  • Scattered areas of fibro-glandular density indicates there are some scattered areas of density, but the majority of the breast tissue is non-dense. About 4 in 10 women have this result.

  • Heterogeneously dense indicates that there are some areas of non-dense tissue, but that the majority of the breast tissue is dense. About 4 in 10 women have this result.

  • Extremely dense indicates that nearly all of the breast tissue is dense. About 1 in 10 women have this result.

In general, a woman whose breasts are classified as heterogeneously dense or extremely dense is considered to have dense breasts.

About half (!) of women undergoing mammogram testing have dense breasts.

What causes dense breast tissue?

It's not clear why some women have a lot of dense breast tissue and others do not, but you may be more likely to have dense breasts if you:

  • Are younger. Women in their 40s and 50s are most likely to have dense breast tissue. Your breast tissue tends to become less dense as you age, though some women may have dense breast tissue at any age.

  • Are premenopausal. Premenopausal women are more likely to have dense breasts due to hormone changes.

  • Take hormone therapy for menopause. Women who take combination hormone therapy to relieve signs and symptoms of menopause are more likely to have dense breasts.

Why does breast density matter?

Having dense breasts can affect you in two ways:

  • Increases the chance that breast cancer may go undetected by a mammogram, since dense breast tissue can mask a potential cancer

  • Increases your risk of breast cancer, though doctors aren't certain why

How does dense breast tissue affect mammography breast cancer screening?

  • Dense breast tissue makes it more difficult to interpret a mammogram, since cancer and dense breast tissue both appear white on a mammogram. Very dense breasts may increase the risk that cancer won't be detected on a mammogram.

  • Women with very dense breasts who develop breast cancer are more likely than those with very fatty breasts to have their cancer discovered after a recent normal mammogram.

Source: Mayo Clinic

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