What do you do once you're diagnosed?

The first thing will be to make sure that your imaging is accurate. That may include getting a magnified version of your mammogram or extra tests, such as an ultrasound, X-ray, or MRI. From there, your doctors will want a sample of whatever it is they've identified in your mammogram. "That is best done by freezing [the area] with local anesthetic and putting a needle through the skin into the area designated by the imaging," Dr. Thompson explains. "The key thing is to take sufficient samples to make sure there isn’t anything invasive going on."

Once your doctor has a better idea of what's going on, you may need surgery. That could be a lumpectomy or a more major mastectomy. Dr. Thompson says there's a growing movement among doctors to make sure only those who really need surgery are going through it. Some women may be able to leave their DCIS alone, but should still go in for regular surveillance check-ups.

Then, if you decide to do surgery, you may also have radiation therapy. And finally, to prevent the cancer from recurring or another cancer from developing, Dr. Thompson says you may be prescribed drugs that block estrogen.

How do you decide what to do?

"We used to think of DCIS as a single condition, but it’s a spectrum," says Dr. Thompson. "There are some that can sit in the breast for decades and not do anything, but others can progress into an invading breast cancer."

At this point we're still learning how, exactly, to decipher which is which. But Dr. Thompson says there are trials happening in Europe that will shed some light. For now, ultimately, the decision to move forward with surgery should be up to you and your doctor, and it will depend on your unique situation.

What are the risk factors for DCIS?

Risk factors, aside from simply being a woman, are pretty limited. But we do know that drinking alcohol, not exercising, and eating a poor diet put you at a higher risk for breast cancer in general. Also, as we age and our breast tissue changes, DCIS becomes more common, Dr. Thompson explains. He also says there are some inherited genetic traits that might make it more likely for us to develop DCIS. But, overall, no one's really sure why some get it and some don't.