Frequently Asked Questions About
Hereditary Breast Cancer
All cancer involves changes in genes called mutations. However, in most people,
these changes occur after birth, usually later in life and only in a limited number of
the body’s cells. Hereditary cancer refers to cancer that is caused by a mutation
that is present at birth and in all cells of the body. This gene change makes
individuals more likely to develop cancer in their lifetime but doesn't mean they will
definitely develop the disease. Certain cancers, including those of the breast, ovary,
and colon, are more likely than others to be hereditary.
This fact sheet will answer questions on hereditary breast cancer. It might not
answer all your questions because the issue of hereditary breast cancer is very
complex. We have provided a listing of helpful resources at the end of this sheet
where you can get more information. If you are concerned that you are at increased
risk for breast cancer due to your family history, please contact a genetic counselor
in your community.
How common is hereditary breast cancer?
Approximately 10% of breast cancer is considered "hereditary.” The majority of
breast cancers, however, are called “sporadic,” meaning we don’t know why they
How can I determine if the breast cancer in my family is hereditary?
Important factors in determining if the breast cancer in a family is hereditary
include: the age of onset of breast cancer; the presence of certain other types of
cancer in a family; and the number of relatives with cancer and their relationship to
you. A genetic counselor will look at your family’s medical information (called a
pedigree) including the medical information on first-degree relatives (parents,
siblings, and children), second-degree relatives, (grandparents, aunts, and uncles),
and third-degree relatives (cousins).
Two of my close relatives have had breast cancer. Does that mean that I
will get breast cancer too?
Having two relatives on