Narrator: This is Science Today. Ductal carcinoma in situ, or DCIS, is a non-invasive form of breast cancer and accounts for twenty percent of all newly diagnosed cases of the disease in the United States. Dr. Karla Kerlikowske of the University of California, San Francisco says it's a type of breast lesion that's contained within the milk ducts.
Kerlikowske: Genetically, it's fairly advanced having lots of genetic changes that look like invasive cancer, but the thing that makes it interesting is that not everyone who has those lesions goes on to get invasive cancer. So, some people look at it as a precursor of invasive cancer. Some people think it's just a marker or a risk factor for those who will get invasive cancer.
Narrator: Prior to mammography being introduced in the Eighties, Kerlikowske says DCIS was very uncommon.
Kerlikowske: And that's because it's rare to present as a breast lump. And since the advent of screening mammography, the incidence has gone up four, to five, six hundred percent, some people say.
For Science Today, I'm Larissa Branin.