Ductal Carcinoma In Situ of the Breast

Context.-In situ carcinomas of the breast constitute 15% to 30% of all newly diagnosed breast cancer cases; 80% of these in situ lesions belong to the ductal carcinoma in situ (DCIS) category. Similar to invasive breast carcinomas, DCIS is not a single disease but rather many distinct diseases with different histopathologic and molecular characteristics, a propensity to progress to invasive disease, and differential response to treatment. Objective.-To review the classic pathologic parameters of clinical significance and the differential diagnosis of the DCIS lesions, present our new understanding of the importance of biomarkers, and discuss innovative approaches for targeted therapy in DCIS. Data Sources.-Extensive review of the relevant peerreviewed literature. Conclusions.-In DCIS, improved understanding of the underlying biologic pathways of tumor progression is expected to lead to more accurate classification and innovative targeted treatment approaches for the management of these lesions.