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Ductal carcinoma in situ (DCIS) of the breast is a heterogeneous group of lesions with diverse malignant potential and a range of treatment options. It is the most rapidly growing subgroup among breast cancers, with more than 68,000 new cases diagnosed in the United States during 2008 (27% of all new cases of breast cancer).1 More than 90% are nonpalpable and discovered mammographically.
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It is now well appreciated that DCIS is a stage in a neoplastic continuum in which most of the molecular changes that characterize invasive breast cancer are already present.2 Only quantitative changes in the expression of genes that have already been altered separate DCIS from invasive growth. Genes that may play a role in invasion control a number of functions, including angiogenesis, adhesion, cell motility, the composition of extracellular-matrix, and more. To date, genes that are uniquely associated with invasion have not been identified. DCIS is clearly the precursor lesion for most invasive ductal carcinomas, but not all DCIS lesions have sufficient time or the genetic ability to progress to invasive disease.3-5
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Therapy for DCIS ranges from simple excision to various forms of wider excision (segmental resection, quadrant resection, oncoplastic resection, etc.), all of which may or may not be followed by radiation therapy. When breast preservation is not feasible, total mastectomy, with or without immediate reconstruction, is generally performed.
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Since DCIS is a heterogeneous group of lesions rather than a single entity,6,7 and because patients have a wide range of personal needs that must be considered during treatment selection, it is clear that no single approach will be appropriate for all forms of the disease or for all patients. At the current time, treatment decisions are based upon a variety of measurable parameters (tumor extent, margin width, nuclear grade, the presence or absence of comedonecrosis, age, etc), as well as physician experience and bias, and upon randomized trial data, which suggest that all conservatively treated patients should be managed with postexcisional radiation therapy.
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There have been dramatic changes in the frequency, clinical importance, and treatment of DCIS in the past 30 years. Before mammography was common, DCIS was rare, representing less than 1% of all breast cancer.8 Today, DCIS is common, representing 27% of all newly diagnosed cases and as many as 30% to 50% of cases of breast cancer diagnosed by mammography.1,9-13
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Previously, most patients with DCIS presented with clinical symptoms, such as breast mass, bloody nipple discharge, or Paget disease.14,15 Today, most lesions are nonpalpable and generally detected by mammography alone.
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Until approximately 20 years ago, the treatment for most patients with DCIS was mastectomy. Today, almost 75% of newly diagnosed patients with DCIS are treated with breast preservation.16 In the past, when mastectomy was common, reconstruction was uncommon; if it was performed, it was generally done as a ...