BACKGROUND: Ductal carcinoma in situ (DCIS) is detected more often since the advent of mammography. A standardized pathologic staging and grading system does not exist, but nuclear grade is assuming greater importance. The history of DCIS is long, and its treatment is a controversial issue in breast cancer today. METHODS: Data have been reviewed regarding the role of HER-2 expression as a prognostic variable, as a predictive factor for response to chemotherapy and hormonal therapies, and as a directed therapeutic target for breast cancer. RESULTS: The NSABP protocol B06 revealed a recurrence rate of 43% in patients treated with local excision alone. Half of recurrences are still DCIS, but 50% are invasive. Local control is markedly improved by the addition of radiation. Recurrence is also minimized by careful cytologic review of margins. Sentinel lymph node biopsy has resulted in more accurate nodal staging. CONCLUSIONS: As a heterogeneous lesion, DCIS may not lend itself to a uniform treatment approach. Careful analysis of resection margins is required. As our understanding of the diagnosis and treatment of this disease develops, a coordinated team approach is optimal.