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Breast Cancer - Causes and Risk Factors


Information on the author and / or the specialist advisor can be found at the end of the article.

As with most cancers, the root causes of breast cancer are not known. However, some risk factors are known. The most important are:

  • Situations with hormonal imbalance or hormone therapy
  • high mammographic density
  • Smoke
  • Food composition, e.g. high fat diet
  • Inheritance
  • Alcohol consumption
  • Obesity and type II diabetes
  • little physical activity
  • Radiation of the chest in childhood (e.g. with lymphoma)


Whether, how often and at what age women have children also has an impact on the development of breast cancer, as does whether and for how long the children were breastfed. The onset of menstruation and menopause and thus the total number of menstrual periods are also factors that determine the risk of the disease.
Rumors can be found especially on the Internet, but also in newspapers and magazines, that breast cancer is also triggered by bras that are too tight, deodorants containing aluminum, breast implants or even abortions. However, these are "cancer myths" and these claims are without any scientific basis.

Female hormones (estrogen, progesterone)

The cells in the breast have what are known as receptors that can bind hormones (e.g. estrogens) to themselves. This is how “messages” get into the cell through hormones. Among other things, it stimulates the growth of the gland cells in the breast during puberty or pregnancy. Unfortunately, estrogens can also promote the development and multiplication of some cancer cells via these receptors. This applies in particular to preparations for menopausal symptoms ("hormone replacement therapy").

Hormone replacement therapy increases the risk of breast cancer if it is used for more than five years, especially with preparations that contain both estrogen and progestin. If the hormones are stopped, the risk drops back to the average level within a few years.

Unhealthy lifestyle

Smoking is the most important preventable risk factor for cancer - this applies not only to lung cancer, but also to many other types of cancer - including breast cancer. In particular, when girls start smoking in their teens, their risk of breast cancer increases significantly. The alarming increase in lung cancer among women should be a reason not to smoke at any age.

Diet also plays a role in terms of quantity and composition: overweight people get breast cancer more often than lean women, because hormones are formed in adipose tissue that raise the level of estrogen. And the fat in the food also plays a role: Those who eat a lot of animal fats (fatty sausage and fatty meat, whole milk products, butter, lard) also have a higher estrogen level and thus a slightly higher risk. This explains, among other things, the much lower incidence of breast cancer in Asian countries, where traditionally only little animal fat is eaten. Due to the increasing adaptation to Western habits, however, the risk of breast cancer is now also increasing in Asia.

Density of the mammary gland

Women with a high so-called mammographic density - i.e. with less fat and more glandular and connective tissue - have a five times higher risk of developing breast cancer. For comparison: women who have a first-degree relative developed breast cancer are approximately twice as likely to have breast cancer.
The density of the breast can be determined on the basis of mammography images and is divided into four different degrees of density depending on the ratio of the denser connective and glandular tissue to the less dense fatty tissue:
- Density level I: fat transparent, well transparent,
- Density grade II: moderately transparent,
- Density III: tight,
- Degree of density IV: extremely dense.

Mammographic density is influenced by a number of factors. For example, hormone replacement therapy can increase density through the influence of estrogen.

Hereditary breast cancer

Around five to ten percent of all breast cancer cases are hereditary. If breast and ovarian cancer occur more frequently in a family, genetic counseling in a special consultation hour for familial breast and ovarian cancer can provide clarification. If the suspicion of a hereditary problem is confirmed, a genetic test should be considered. Hereditary breast cancer can be triggered by changes (mutations) in the BRCA-1 and BRCA-2 genes; but there are also other “breast cancer genes”. Depending on the result of the genetic testing and individual risk calculation, participation in a so-called intensified early detection for breast cancer can be offered in many cases.

Breast cancer risk check

If you answered yes to at least two questions from checklist 1 or at least one question from checklist 2, you should take the screening tests seriously. Talk to your gynecologist about it.

Risk check 1

  • Were you under 11 years old when you had your first menstrual period?
  • Were you over 54 years old when you last menstruated?
  • Are you childless?
  • Did you have your first child when you were over 30 years old?
  • Did you not breastfeed, or only for a short time?
  • Are you clearly overweight?
  • Do you usually have little exercise?
  • Do you drink plenty of alcohol (more than a small glass of beer or wine a day on a regular basis)?
  • Have you been taking hormones for menopausal symptoms for at least five years?

Risk check 2

  • Do you have or have you ever had breast cancer?
  • Have you been diagnosed with ovarian, uterine or colon cancer in the past five years?
  • Do you have pronounced mastopathy (changes in the mammary gland with lumps and cysts)?
  • Has a tissue sample been taken from your breast because of an unclear finding?
  • Does more than one relative (grandma, mother, daughter, sister) have breast cancer and / or ovarian cancer?



AGO Recommendations Gynecological Oncology Commission as of March 2017 at: https://www.ago-online.de/leitlinien-empfänger/leitlinien-empfänger/kommission-mamma

Expert advice:

Prof. Dr. Fehm University Women's Clinic in Düsseldorf
Prof. Dr. Scharl Clinic Amberg
Prof. Dr. Lux University Women's Clinic Erlangen


Newsletter dispatch via www.CleverReach.de

Last content update on: May 19, 2017

More information on breast cancer:

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Read more Hereditary Breast Cancer - When Cancer Is in the Genes

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Read more Breast Cancer Follow-Up Care

Last accessed on: May 20, 2021 11:36 am