A day in the life with Kathryn Malherbe

I have dense breast tissue…but what does it mean?

A popular topic in the latest breast cancer research has been the relation between dense breast tissue and the increased risk to develop breast cancer, 5-10% to be exact. Many women are told during a mammogram examination that they have dense breast tissue and are at a higher risk, but what exactly does that mean?

On a mammogram, breast tissue is depicted as varying shades of grey. The appearance of the breast tissue amongst women varies and is also seen as variations in the composition on a mammogram. Fatty tissue is dark grey and known as lucent (see-through). Connective and epithelial tissue (the glandular part of your breast) is white and known as dense.

When your doctor is referring to your ‘dense’ breast tissue, on a mammogram report, they’re referring to the glandular (white) component seen on the image. The denser the breast tissue, more white components are seen, and because it is so dense, it is difficult to ‘see through it’.

Cancerous solid tumors in the breast sometimes also appear as white star-shaped nodules, and micro-calcification (small white groups of specks) are also depicted as white on a mammogram, so in-between all your dense breast tissue, there may be similar dense white abnormalities hiding in-between the breast tissue, thus making it hard to visualise the cancer. From a radiological point of view, the sensitivity rate of detecting breast cancer in a dense breast can reduce from 97-98% to 85-87%.

Younger women have naturally denser breast tissue. This is normal and expected for their age group, and as a woman ages, the glandular dense tissue will gradually involute (change) to a fattier type consistency. This, however,  is not true for women who are on hormone replacement therapy (HRT) as this can cause the density of the breast to remain the same as women age.

There are five types of breast tissue:
Type I: Most common type of breast tissue in pre-menopausal women.
Type II: Fatty type breast tissue.
Type III: Like Type II, the breast is fatty, but has a few visible ducts on the mammogram.
Type IV: See nodules and densities (moderate dense type breast tissue).
Type V: Dense breast tissue.

Normally, most women over 40 years have a common Type II breast tissue. In women over 50 years, Type V breast tissue is less common. The prevalence (how many is seen in a group) of breast cancer in women with Type IV-V breast tissue is more than women with Type I-III breast tissue.

A woman between the ages of 40-54 with a Type IV-V breast tissue has the same risk of developing breast cancer as a woman aged between 55-69 years with a Type I-III breast tissue. Having said that, a woman between the ages of 55-69 years may take a time period of over 15 years to develop the same breast cancer risk as a woman that has a Type IV-V breast tissue.

Another concept is that dense breast tissue has a higher ratio of physiologically active glandular and lobular components, thus there is more tissue that is actively changing, and a higher chance that this dense tissue might have abnormal changes as well.

What can you do to reduce your risk of developing breast cancer if you have dense breast tissue?
  • Have an annual mammogram done.
  • Know and understand the importance of monthly breast self-examinations.
  • If you have a strong first-degree maternal family history or you were diagnosed with Hodgkin’s lymphoma as a child, your risk for developing breast cancer is slightly higher and the possibility of an annual MRI evaluation as adjunct to the annual check-ups is advised.
  • More recently, radiologists refer patients for an MRI if the patient has heterogeneously dense breast tissue to ensure that nothing is missed.

Meet our expert - Kathryn Malherbe

Kathryn Malherbe is a senior mammographer working at LaVita Women’s Wellness Centre in Pretoria. She is currently working on her Master’s degree, which focuses on lobular carcinoma of the breast, and the diagnosis thereof can be improved with ultrasound detection tools.

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