Ductal carcinoma in situ: biology, diagnosis, and new therapies.

The incidence of ductal carcinoma in situ (DCIS) has markedly increased as a result of the use of screening mammography. Whether DCIS is a premalignant lesion or a cancer remains a cause of debate, but evidence supports the idea that DCIS evolves into invasive breast cancer based on histologic patterns, similar risk factors, and genetic similarities. Microcalcifications identified during mammography generally raise the suspicion of DCIS, and biopsy, often by core needle, confirms such a diagnosis. The extent of disease can be further delineated by breast magnetic resonance imaging. Radiation therapy in breast-conserving treatment, along with tamoxifen, decreases the overall rate of local recurrence in patients with DCIS. Studies in the treatment of DCIS exploring partial breast radiation and trastuzumab are under way. Ongoing investigations with comparative genomic hybridization suggest that there are independent, evolutionary genetic pathways within DCIS. Genome-wide microarray-based gene expression analyses are now providing new opportunities to discover genes that are specifically activated or inactivated during the course of breast cancer progression.