First, don’t panic. The odds are in your favor; a whopping 90 percent of lumps are noncancerous, so chances are, yours is not serious.

But don’t let that statistic lull you into a false sense of security either. Anytime you feel a lump or see or feel any unusual changes in your breasts, call your doctor immediately and set up an appointment. Because lumps can sometimes come and go with your menstrual cycle, she may schedule your checkup a few weeks later, having you monitor the area in the meantime to see if the lump disappears on its own.

When you do see your doctor, she will perform a clinical breast exam with her hands, and if necessary, follow up with an ultrasound, a needle biopsy or an MRI. Those tests will reveal whether the lump is, say, a benign cyst -- a noncancerous sac filled with water -- or something more serious. If it is the former, keep an eye on it and see your doctor again if you notice any changes or additional lumps.

Your Expert

Debbie Saslow, Ph.D., is the director of breast and gynecologic cancer at the American Cancer Society.