A breast self-exam only takes a few minutes each month, and it could save a woman's life.

The important thing to remember with self-exams is consistency, says Shaparak Kamarei, M.D., USC associate clinical professor of internal medicine.

"The breasts should be examined at the same time of month every month because the breast glands change in size over the monthly cycle," says Kamarei. "Mark the date on your calendar."

The self-exam should be done two weeks from the beginning of menstruation, when the breasts are least swollen and any abnormalities are easier to detect, she adds.

Although women find 90 percent of breast lumps on their own, researchers estimate that only 33 percent of women actually perform routine breast self exam.

There are three ways to examine your breasts.

Lying down
Lying on your back, place a pillow under your right shoulder. Put your right hand under your head. Move your finger pads in a spiral motion over your entire right breast and in your armpit. Change the pressure to feel the different tissue layers. Some women use lotion help their hands slide over the breast. Repeat with the left breast.

Before a mirror
Look for changes in the shape or skin texture of your breasts. Check them with your arms at your side, arms overhead, hands pressing on hips and bending forward. Gently squeeze the nipple. If there is a discharge, have it checked by your doctor.

In the shower
Raise your arms and check breasts with soapy fingertips, using the technique described previously.

If you find a lump, don't panic. Most breast lumps are harmless cysts, which are fluid-filled sacs, Kamarei says. Cysts change in size and feel soft and rubbery. In contrast, breast cancer feels like a painless pebble, which can move around or be stuck to the breast tissue. Cysts often enlarge and become tender just before your menstrual period.

For some women, a lump is normal. But only a professional check-up can determine if it is cancerous or not.