Ductal carcinoma in situ (DCIS) is a non-obligate precursor to invasive breast cancer. Although there is extensive information on the cellular and molecular changes in DCIS, there is limited ability to functionally test. The critical changes in premalignant progression. This review summarizes our experience with a recently developed method which provides. The opportunity to functionally test the molecular events occuring to functionally test the molecular events occurring in the initial changes in premaligant progression; i.e., the step from non-invasive to invasive behavior.