Top 10 Breast Cancer Risk Factors

by PJ Hamel Patient Expert

Don't drink. Lose weight. Don't fight those hot flashes with hormone replacement therapy. Yadda yadda yadda" You've heard it all before, right? Considering the amount of breast cancer prevention information with which we're constantly assailed, it's easy to become confused. With a nod to the American Cancer Society's recently published "Breast Cancer Facts & Figures 2007-2008," following are the current top-10 risk factors for breast cancer.

Highest risk factors:

1. Being female. OK, you knew that. This year, an estimated 240,510 American women will be diagnosed with breast cancer (either invasive, or in situ). About 2,030 American men will be diagnosed with breast cancer, accounting for less than 1% of all breast cancers. The X chromosomes win this one.

2. Your age. If you're older than 65, you're at greater risk than those younger than 65. And your risk will continue to increase until you're 80 years old, at which time it levels off. An American woman's lifetime risk of developing breast cancer is 1 in 8 (12.3%). But that's lifetime risk, not your current risk. If you're 20 years old, your actual risk of getting breast cancer right now is 1 in 1,837. At age 50, your risk is 1 in 40, and at age 60, 1 in 28.

3. Carrying the BRCA1 or BRCA2 genes. 5% to 10% of all breast cancers are a result of inherited mutations in these two genes; women with them run a 45% to 65% risk of developing breast cancer by age 70. Thankfully, less than 1% of American women carry these genes. Genetic testing for BRCA1 and BRCA2 is available, but only recommended for women who already show a family history of the disease, or at the recommendation of a genetic counselor for some other specific reason. So don't go out and try to get tested just to set your mind at ease; it's not necessary.

4. Two or more first-degree relatives (mother, sister, or daughter) diagnosed with breast cancer at an early age (generally, below age 50). The more first-degree relatives and the younger their age of diagnosis, the greater your risk factor.

5. Personal history of breast cancer. If you've already had breast cancer, you know the drill: mammograms, regular physicals, and an awareness of risk factors (plus working to lessen those factors you can control) will be part of your life from now on.

6. Dense breasts. This one has continued to gradually creep up the list, as researchers draw more and more connections between dense breasts and breast cancer. Breast density isn't something you can identify yourself; it needs to be done by a radiologist reading your mammogram. If you're concerned, ask your PCP or oncologist how you can find out if you have dense breasts. In general, women with large breasts (more fat tissue in relation to gland tissue) don't have dense breasts; small-breasted women are much more at risk for the condition.

7. Atypical hyperplasia. This is a condition detected via biopsy. Perhaps you felt a lump or thickening, had a biopsy done, and were told the lump wasn't cancerous, but that it exhibited "atypical hyperplasia." This is an overgrowth of abnormal-appearing cells in the ducts and lobules of the breast. They're not cancer cells" but neither are they normal. They're somewhere in between, with a risk of developing into cancer cells. Kind of like, it's not raining yet, but those dark clouds sure look ominous"

Next-highest risk factors:

8. One first-degree relative with breast cancer. See #4, above.

9. High-dose radiation to the chest. If you had high-dose radiation therapy to your chest area before the age of 30, usually as a result of Hodgkins disease, this increases your risk of developing breast cancer. Thankfully, this represents a small percentage of the population.

10. High bone density. There's an established link between dense breasts (see #6, above) and high bone density. Researchers aren't sure how that connection makes high bone density a risk factor; only that it seems to do so. Note that high bone density is a risk factor only for postmenopausal women, which is problematic: do we try to keep our bone density high to prevent osteoporosis and broken bones? Or do we strive to keep it lower to help prevent breast cancer? Considering the relative risk of each, my personal opinion would be to continue taking those calcium pills.

And there you have it, the American Cancer Society's current top-10 breast cancer risk factors. Just to finish off the list, here are the remaining, less influential (but still proven) risk factors.

The following factors increase the level of circulating hormones in your body, which has been shown, in turn, to increase your risk for breast cancer:

  • Having your first child after age 30;

  • Starting your period before age 12;

  • Going through menopause after age 55;

  • Never having had a child*;

  • Never having breast-fed a child;

  • Recent oral contraceptive use (10 years after discontinuing, the risk disappears);

  • Recent and long-term hormone replacement therapy (HRT);

  • Postmenopausal obesity. If you've gained 55 pounds or more since age 18, you're 1 1/2 times more likely to get breast cancer than those women who've maintained their weight. If you gain 22 pounds or more after menopause, you have almost a 20% greater risk of getting breast cancer than those women who maintain their pre-menopause weight.

*A just-released study suggests a specific link between pregnancy and breast cancer prevention (other than hormone levels). During pregnancy, some of your baby's cells can migrate into your bloodstream, and then live there for years; women with a greater number of these cells seem to be at less risk for breast cancer. Researchers hypothesize that your child's cells are seen by your immune system as abnormal. And that these abnormal cells continue to keep the immune system on alert, and thus more likely to find and destroy cancer cells before they proliferate. Interesting, huh?

Finally, here are the remaining (lowest) risk factors on the ACS list:

  • A history of endometrial, ovarian, or colon cancer;

  • Drinking alcohol. Researchers aren't yet sure how much is too much, but it could be as little as a single drink. Think about it.

  • Being tall. What's the connection? Researchers don't yet know, only that there seems to be a link.

  • Higher socioeconomic status.

  • Being Jewish.

If you haven't had breast cancer and want to estimate your own personal risk of developing it, check out the National Cancer Institute's online risk assessment tool.

PJ Hamel
Meet Our Writer
PJ Hamel

PJ Hamel is senior digital content editor and food writer at King Arthur Flour, and a James Beard award-winning author. A 16-year breast cancer survivor, her passion is helping women through this devastating disease. She manages a large and active online survivor support network based at her local hospital and shares her wisdom and experience with the greater community via