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My mom had ovarian cancer. Am I in danger?

Family history is very important in predicting diseases. Dr. Judith Reichman has details on the genes that can transmit cancer.

Q: My mother died of ovarian cancer in her early 50s. Her three sisters are now in their 80s and show no evidence of this disease. Do I have a “family history” of ovarian cancer?

A: Yes, you do.

Having just one first-degree relative — your mother — who developed this horrific disease at such a young age does constitute a family history.

More than 90 percent of ovarian cancers are not genetic and usually occur after age 60. But your mother’s early-onset ovarian cancer may have been from a genetic mutation in one of her BRCA genes. Given that she died so long ago, it was probable that she was not tested, so you cannot know for sure, but if she did have the mutated gene you run a 50 percent chance of having it, too.

Each of us shares 50 percent of our genes with our first-degree relatives — parents, siblings and children.

We share 25 percent of our genes with second-degree relatives — grandparents, aunts, uncles, nieces and nephews.

And we share 12.5 percent with third-degree relatives — great-grandparents, cousins, etc.

This includes ancestors and progeny on both sides of your family — your father’s as well as your mother’s.

It’s true that each of the sisters had the same chance as you mother of inheriting this mutation. But it appears that none of them did — or that the gene has not expressed itself.

To know for sure whether you have inherited a BRCA mutation, you can have your blood tested. If you are descended from Jews of Eastern European (Ashkinazi) origin, the test would look at three mutation sites commonly found in this ethnic group and cost less than $400.

Otherwise, the test would need to look at all possible mutations, which would run several thousand dollars and might or might not be covered by insurance.

For more information, you can visit the web site of Myriad Genetic Laboratories (myriadtests.com), which has the patent on the test.

A positive BRCA mutation means a lifetime risk of up to 40 percent for ovarian cancer. Your mother’s history also raises concern about breast cancer. Women with the BRCA mutation have a lifetime risk of up to 80 percent for breast cancer (BRCA is an acronym for breast cancer) and an increased risk of colon or pancreatic cancer.

Testing for the BRCA mutation is reasonable if:

  • you have a first- second- or third-degree relative on either side who developed ovarian cancer at any age.
  • You have a first-degree relative who developed breast cancer before age 50.
  • You have two or more first- or second-degree relatives who developed breast cancer before 50 or ovarian cancer at any age.
  • You have one first-, second- or third-degree relative who has tested positive for a BRCA mutation.
  • You yourself developed breast cancer before 50 or had ovarian cancer at any age.
  • You have a first- second- or third-degree male relative who developed male breast cancer.

Dr. Reichman’s Bottom Line: If you have just one first-degree relative with ovarian cancer, you are at risk — and this knowledge can help with decisions about detection and prevention.

Dr. Judith Reichman, the “Today” show's medical contributor on women's health, has practiced obstetrics and gynecology for more than 20 years. You will find many answers to your questions in her latest book, "Slow Your Clock Down: The Complete Guide to a Healthy, Younger You," published by William Morrow, a division of .

PLEASE NOTE: The information in this column should not be construed as providing specific medical advice, but rather to offer readers information to better understand their lives and health. It is not intended to provide an alternative to professional treatment or to replace the services of a physician.