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Cancer Genetics

Breast Cancer Risk



How would the following family history affect my breast cancer risk? All the people are on my father`s side of the family.

2 aunts breast cancer in their 40s, 1 uncle prostate cancer in his 50s, 1 great aunt (my grandfather`s sister) breast cancer in her 30s, 1 great-grandmother (my grandfather`s mother) breast cancer (don`t know what age).


This family history is suspicious for the kind of family in which cancers appear to be inherited as an autosomal dominant trait.  This means that each child of a woman with breast cancer will have a 50% chance of inheriting the "cancer susceptibility trait".  However, inheriting a "cancer susceptibility trait" does not invariably mean that child will develop cancer.  In many of the cancer susceptibility syndromes, we see that there is reduced penetrance.  This means that less than 100% of people who inherit the trait will develop cancer.  Sometimes this may be as low as 45-50%, and sometimes it may be quite a bit higher.

Because you have three generations of women who have developed breast cancer, with at least three women with breast cancer before the onset of menopause, this family history has many of the signature features we look for in inherited cancer families.  A consultation with a genetic counselor and/or cancer geneticist would be appropriate.

Genetic testing will potentially help identify who in the family is at increased risk, and who is not at increased risk.  Even though everyone is on your father's side of the family, your risk of breast cancer may be increased simply on the basis of the family history.  A genetic counselor can discuss this information in more detail with you, and use computer models to help you decide whether there are changes in your screening that might be helpful, or whether other options might be appropriate to reduce the risk of breast cancer.

To find a genetic counselor in your area, please go to the NSGC website attached to this message.  You can get additional information about breast cancer risk and screening by visiting the website for the National Cancer Institute listed below.


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Response by:

Duane D Culler, PhD, MS Duane D Culler, PhD, MS
Clinical Instructor of Genetics
School of Medicine
Case Western Reserve University