The panel of 9 stakeholders expanded the initial list of 20 evidence gaps to 30 and identified several common themes relevant to the evidence gaps. The overarching theme behind most comments was that there is considerable uncertainty about diagnosis (that is, whether the condition is truly limited to DCIS or whether there are areas of invasive cancer), prognosis (that is, the likelihood that a given DCIS lesion in a given patient will progress to life-threatening invasive cancer if left untreated), and treatment (that is, the likelihood that a given treatment option will prevent the development of life-threatening invasive cancer, whether that likelihood will change based on specific patient or tumor characteristics, and whether the reduction in risk is enough to justify the potential undesirable outcomes of that treatment). Given this uncertainty, stakeholders emphasized the need for comparative studies of techniques for improving diagnostic certainty (that is, the comparative sensitivity and specificity of different imaging methods to guide pathologic diagnosis and surgical planning) and prognostic certainty, particularly for identifying DCIS lesions that are least likely to progress to life-threatening invasive cancer. Stakeholders also stated that there is a need to assess decision-support interventions to manage uncertainty about the short- and long-term implications of a DCIS diagnosis, how DCIS differs from invasive breast cancer, and the relative harms and benefits of different management options. There was particular interest in evaluating strategies, such as peer-to-peer support or lifestyle modifications.