Ductal carcinoma in situ: challenges, opportunities, and uncharted waters.

Ductal carcinoma in situ (DCIS) is a heterogeneous group of diseases that differ in biology and clinical behavior. Until 1980, DCIS represented less than 1% of all breast cancer cases. With the increased utilization of mammography, DCIS now accounts for 15% to 25% of newly diagnosed breast cancer cases in the United States. Although our ability to detect DCIS has radically improved, our understanding of the pathophysiology and factors involved in its progression to invasive carcinoma is still poorly defined. In many patients, DCIS will never progress to invasive breast cancer and these women are overtreated. In contrast, some DCIS cases are clinically aggressive and the women may be undertreated. We are able to define some of the predictors of aggressive DCIS compared with DCIS of low malignant potential. However, our ability to risk-stratify DCIS is still in its infancy. Clinical risk factors that predict aggressive disease and increased risk of local recurrence include young age at diagnosis, large lesion size, high nuclear grade, comedo necrosis, and involved margins. Treatment factors such as wider surgical margins and radiation therapy reduce the risk of local recurrence. DCIS represents a key intermediate in the stepwise progression to malignancy, but not all aggressive breast cancers appear to have a DCIS intermediate, notably within triple-negative breast cancer. Ongoing studies of the genetic and epigenetic alterations in precancerous breast lesions (atypia and DCIS) as well as the breast microenvironment are important for developing effective early detection and individualized targeted prevention.