In this blog post I want to give you some more information about the breast cancer genes that are known and about heredity. There is a lot of information but as a former doctor I want to explain you briefly in understandable language.


Usually (90-95%) breast cancer is not hereditary. However, if:

  • in a family several women (and possibly men) get breast cancer,
  • whether breast cancer develops at a young age (under 40),
  • whether breast cancer develops in several places (for example in 2 breasts)
  • and / or whether ovarian cancer occurs in a family,

then there may be a hereditary mutation. If there are questions about whether or not hereditary breast cancer is involved, a clinical geneticist is often referred. This doctor often checks with the patient, who in the family became ill and at what age and possibly DNA testing is done.


The two genes that have known the longest are the BRCA1 and BRCA2 genes. BRCA stands for BReast CAncer. The chance that a woman with a mutation in the BRCA1 or BRCA2 gene before the age of 80 develops breast cancer is around 60 to 80%. The risk of ovarian or ovarian cancer before the age of 70 is 35 to 45% with a BRCA1 mutation and 10 to 20% with a BRCA2 mutation. However, men also have an increased chance of developing breast cancer, but this is much lower than in women. Men with a BRCA1 gene have a 3% chance and with a BRCA2 gene 7%. In addition, men with a BRCA2 mutation have a greater chance of prostate cancer, namely 15 percent. Persons of Ashkenazi Jewish descent appear to have an increased 1 in 40 chance of carrying a BRCA gene mutation. Everyone inherits a part of father and mother from this gene. The mutation can therefore also be given by men and women.

The CHECK2 gene.

In Western Europe, the CHECK2 * 1100deIC mutation is common in the CHECK2 gene. In families with a lot of breast cancer you often see that the mutation also occurs more often, namely in 5% of the cases compared to 1% in families without breast cancer. A woman with the CHECK2 gene and breast cancer also has an increased risk of getting breast cancer in the other breast. You also inherit part of your father and mother from this gene. However, if you inherit the CHECK2 * 1100deIC mutation from the father's and mother's side (also known as homozygous), women have a 60-80% chance of developing breast cancer, just like with the BRCA genes. This homozygous CHECK2 mutation may also have an increased risk of colon cancer.

What if a gene mutation has been demonstrated? Then, depending on the gene mutation, you will receive (annual) tests to detect breast cancer at an early stage.

Another option in addition to the annual examinations is a risk-reducing operation, such as the preventive removal of both breasts and / or ovaries. Risk-reducing operations can reduce the risk of breast and ovarian cancer. Women who opt for a risk-reducing operation often do so for fear of getting breast and ovarian cancer. The preventive removal of breasts and / or is often very drastic, even when a breast reconstruction has been done immediately. It is therefore always discussed in consultation with the specialist and patient whether checks and / or preventive operations take place.

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Greetings from Cathalijne