before a biopsy. An ultrasound can often distinguish between a fluid-filled cyst and something else, but not always. (It's the same type of procedure as when they do it on pregnant women to see the baby--it isn't invasive, it's fairly quick, and there's no pain.)

If she's had mammograms for years, and there's a new spot, there could be more reason to check it out. If this is her first mammogram (or first in a long while) then a spot like this could just be a normal part of the breast. Going back in six months is so that if it does start changing, they can still catch it early, and if it doesn't change, they have a good idea that it's harmless.

A biopsy is more invasive. They use local anesthesia, so you're awake the whole time. The nurse is basically doing an ultrasound while the surgeon sticks a long needle-gun into the breast. After guiding the needle to the spot of concern, the surgeon pulls the trigger. The gun shoots out and takes tiny chunks of the breast tissue. After getting the samples, the surgeon injects a tiny piece of gold at the site. This serves as a marker so that when the next mammogram shows the same "spot," the radiologist knows it's already been biopsied. The samples are sent to the lab and screened for cancer. You can see from this why a biopsy isn't recommended for every "spot" that appears on a mammogram.

My experience is that doctors tend to order more tests anytime there's the least reason for concern--if there's a question of whether to test or not, they'll go with getting the test. If they're saying wait six months, they aren't seeing something they're immediately concerned about.

Of course, anytime you hear, "This could be cancer," you want to know immediately. But I would go with your doctor's advice. Making sure she's checking for lumps is always a good thing, and it might give you more peace of mind in the interim.