Can Breast Tumors Disappear on Their Own?

I've seen this story in several newspapers recently, but I think today's USA Today article is easier to read and understand.

We know that one rare type of cancer found through screening sometimes disappears on its own, but in this study, researchers asked: do more invasive breast cancers found in mammograms disappear on their own?

Researchers in Norway and the U.S. compared the number of breast cancers found in more than 100,000 Norwegian women who were screened every two years with an equal number who received only one mammogram after six years.

They found that 22% more breast cancers were discovered among the women who got more frequent mammograms. This discovery raises the possibility that mammograms found cancers that eventually went away, and thus never needed to be treated.

It's important to note that doctors may more easily find cancers on repeat mammograms, and that most doctors believe that frequent mammograms save lives.