The vast majority of breast cancers are not hereditary. Only 5-10% are due to genetic mutation. It is not because there are many cases of cancer in a family that there is automatically a genetic mutation. In addition, there are genetic mutations that do not influence the risk of developing cancer. As my geneticist explained to me, it would be like words that can be written in 2 ways (ex. color or colour).
When to test for hereditary breast cancer ?
The relevance of the search for a genetic mutation is evaluated according to criteria based on the person who could be tested, but also on his or her family, whether maternal or paternal. Here are the ones used at CHUM :
1. More than one member of your family has had breast cancer before the age of 50.
2. Many of your family members have had breast or ovarian cancer.
3. A man in your family has been diagnosed with breast cancer.
4. A woman in your family has been diagnosed with breast and ovarian cancer.
5. A woman in your family has been diagnosed with bilateral breast cancer (in both breasts).
6. You are of Ashkenazi Jewish descent.
7. You are of French-Canadian descent and one of the situations mentioned above applies to you.
Centre hospitalier de l’Université de Montréal
The decision to take the test or not should not be taken lightly. An evaluation with a geneticist is required before the test. In addition, insurance companies and employers may have access to results in Canada. The test itself is a simple blood sample for which it can take several months to get the results. The results are given at a follow-up appointment.
Genetic mutations, risks and transmission
Genetic mutations are not equally distributed throughout the world. Some mutations will be more present in a given population, while others will be almost absent. For another population, the situation will be reversed or different.
In any case, it is important to understand that it is not because a person has a mutation that predisposes them to cancer that they will automatically develop it.
Both men and women can carry a mutation and pass it on to their children. If one of the parents has a mutation, the child has a 50% chance of inheriting the mutation.
Inflammatory breast cancer
We do not know of any genetic mutations that specifically predispose to inflammatory breast cancer (IBC).
- Centre hospitalier de l’Université de Montréal. Les cancers du sein et de l’ovaire. Retrieved from http://www.chumontreal.qc.ca/patients-et-soins/a-propos-du-chum/le-projet-continuum/science/genetique-medicale/les-cancers-du (in French)
- Canadian Cancer Society. Genetic changes and cancer risk. Retrieved from http://www.cancer.ca/en/cancer-information/cancer-101/what-is-cancer/genes-and-cancer/genetic-changes-and-cancer-risk/?region=qc
- Planetesante.ch. Autour du monde, le cancer varie. Retrieved from http://www.planetesante.ch/Mag-sante/Cancer/Autour-du-monde-le-cancer-varie (in French)
- The IBC Network Foundation. October 22, 2015. [Facebook status update]. Retrieved from https://www.facebook.com/talkibc/posts/951016724971664?match=Z2VuZXXM%3D
- ICI.Radio-Canada.ca. Passer un test génétique et risquer de voir le prix de son assurance augmenter drastiquement. Retrieved from http://ici.radio-canada.ca/regions/ottawa/2016/05/03/006-test-genetique-discrimination-canada-assurances.shtml (in French)