Last updated: Apr 15, 2008

Mammograms are low-dose X-rays of one breast at a time achieved by placing them between two plates and squeezing them flat. Most health organizations recommend that women get an annual mammogram starting at age 40, and before that if they're at increased risk for breast cancer.

The procedure

Kim Heier, 42, of Simi Valley, Calif., half-jokingly describes the test like this: "The mammogram is 'Let's see how much flesh we can pull off of your chest and squoosh into this machine—and then hold that pose!'" The pressure only lasts a few seconds per image, but you will be squeezed for multiple views of the breast (and more views if you have breast implants).

The results

While mammograms aren't perfect at detecting cancer (they miss up to 20% of tumors), they do have the advantage of being able to see a tumor when it's small and most treatable—catching cancer before it has spread to the lymph nodes can mean a five-year survival rate of 98%. And sometimes the test can find a cancer neither you nor your doctor can feel with your fingers.

If you, your doctor, or the mammogram (which is read by a radiologist) detect anything abnormal, remember that there's no need to panic. It's probably not cancer. Your doctor will send you for additional tests to pin down what's been found. It could be that the lump turns out to be a noncancerous growth such as a fluid-filled cyst.

Digital vs. film

Digital mammograms produce X-ray images just as traditional film mammograms do, except that the images are recorded, stored, and viewed on a computer, and the procedure exposes you to less radiation. A 2005 study showed that they are significantly better at screening women who are under 50, pre- or perimenopausal, and/or have dense breasts. Unfortunately, digital mammography isn't widely available yet, but more and more facilities are adding the technology.