According to the Robert Koch Institute, breast cancer is by far the most common type of cancer in women with around 71,000 new cases each year. In addition to a family history, a high-fat diet, consumption of alcohol and cigarettes, lack of exercise and dense breast tissue are also risk factors for breast cancer.

A current study shows that many women cannot assess what such risk factors mean - and above all underestimate breast density as a risk factor.

A woman's breast is made up of glandular, fatty and connective tissue. The breasts of women with dense breast tissue or a high breast density consist largely of glandular and connective tissue and contain little fatty tissue. Younger women and those with a lower body weight tend to have denser breast tissue.

But: How high the proportion of fat, connective and glandular tissue in the breast is depends on the hormone level. Because of this, breast density can increase and decrease during the menstrual cycle. During the menopause, breast density decreases in most women because glandular tissue regresses.

How firm or big a breast is has nothing to do with breast density. How dense the breast tissue is cannot be felt, but can only be seen with an X-ray examination (mammography) of the breast. However, due to cycle-related changes, breast density may be assessed differently after multiple examinations.

When the breast is X-rayed, the fatty tissue appears in dark colors in the image - the glandular and connective tissue appears in white in the image. Women with very dense breasts are more likely to miss a tumor on mammography than women with fatty breasts.

Breast density in women is usually divided into four categories ranging from "The breast is composed mostly of fatty tissue" to "The breast is composed almost entirely of glandular and mammary tissue". In a small study from 2000, the authors assume that the accuracy of mammography can drop from 80 percent in the case of a rather fatty breast to just 30 percent in the case of very dense breasts.

Other studies have come to the conclusion that in women with very fatty breasts, almost 100 percent of the tumors are detected during a mammogram. And in women in category 4, i.e. those with the highest proportion of glandular tissue, around 50 percent of the tumors are still detected. In general, mammography is classified as a reliable screening test and many tumors are also detected in women with a high breast density.

According to current knowledge, a high breast density is considered a risk factor in itself. According to current knowledge, the risk of dying from breast cancer for women with increased breast density is not increased. "The part that can lead to cancer in about one in eight women is the glandular part of the breast. Cancer does not develop from the fatty part of the breast, with some rare exceptions," explains Dr. Arif Kamal of the American Cancer Society told Medical News Today.

For women aged 30 to 49 and women aged 70 and over

Once a year, women with statutory health insurance are entitled to have their gynecologist examine their breasts and lymph nodes in their armpits.

Between the ages of 50 and 69

Women in this age group can have mammography screening every two years in addition to palpation. During this examination, an X-ray of the breast is taken to detect tumors.

Women who have a particularly high risk of breast cancer, for example due to genetic predisposition, can have preventive care more often at a younger age.

EU also recommends screening for younger and older women

In the EU, screening guidelines were updated in 2021. The EU guideline now recommends that women between the ages of 45 and 49 and between the ages of 70 and 74 should also have a mammography screening every two or three years.

The researchers of the current study have published their results in the journal "Jama Networks". The researchers interviewed 1,858 women aged 40 to 76 who had no history of breast cancer and who had recently had a mammogram. Study participants were asked to compare breast density to five other risk factors for breast cancer:

"Compared to other known and perhaps better known breast cancer risks, the women did not perceive breast density as a significant risk," Laura Beidler, an author of the study and a researcher at the Dartmouth Institute for Health Policy and Clinical Practice, told CNN. 93 percent of the women surveyed assume that the risk of developing breast cancer is higher if a close relative has cancer than in women with high breast density.

The study authors conclude that denser breast tissue is associated with a 1.2- to 4-fold increased risk of breast cancer, compared to a 2-fold increased risk if a first-degree relative has breast cancer.

However, breast density alone cannot assess a woman's risk of developing cancer. Age and genetic influences play an important role in the development of breast cancer. In other words, a woman's breast cancer risk can only be estimated if all risk factors are considered. A third of those surveyed also said there was nothing they could do to reduce their risk of breast cancer.

Some doctors recommend an ultrasound in addition to mammography for women with a high breast density. This is intended to help tumors that are difficult to identify on the X-ray image to be better detected. However, whether this additional examination makes sense has not yet been scientifically clarified.

The CDC recommends the following to reduce your risk of breast cancer:

Sources: Breast cancer and breast density study, Medical News Today, CNN, health information, burst density and tumor detection study, German Cancer Society 1, German Cancer Research Center, RKI cancer data, Institute for Quality and Efficiency in Healthcare, German Cancer Society 2, CDC