Why the term 'low-grade ductal carcinoma in situ' should be changed to 'borderline breast disease': diagnostic and clinical implications.

During the last several years, increased public awareness, advances in breast imaging and enhanced screening programs have led to early breast cancer detection and attention to cancer prevention. The number of image-detected biopsies has increased, and pathologists are expected to provide more information with smaller tissue samples. These biopsies have resulted in detection of increasing numbers of high-risk proliferative breast disease and in situ cancers. The general hypothesis is that some forms of breast cancers may arise from established forms of ductal carcinoma in situ and atypical ductal hyperplasia, and possibly from more common forms of ductal hyperplasia. However, this is an oversimplification of a very complex process given the fact that the majority of breast cancers appear to arise de novo or from a yet unknown precursor lesion. Currently, atypical ductal hyperplasia and ductal carcinoma in situ are considered as morphologic risk factors and precursor lesions for breast cancer. However, morphologic distinction between these two entities has remained a real issue that continues to lead to overdiagnosis and overtreatment. Aside from morphologic similarities between atypical ductal hyperplasia and low-grade ductal carcinoma in situ, biomarker studies and molecular genetic testing have shown that morphologic overlaps are reflected at the molecular level and raise questions about the validity of separating these two entities. It is hoped that as we better understand the genetic basis of these entities in relation to ultimate patient outcome, the suggested use of the term 'borderline breast disease' can minimize the number of patients who are subject to overtreatment.