Abstract

Ductal carcinoma in situ (DCIS) of the breast is a heterogeneous group of lesions with diverse malignant potential. It is the most rapidly growing subgroup within the breast cancer family with more than 42 000 new cases diagnosed in the United States during 2000. Most new cases are nonpalpable and are discovered mammographically. Treatment is controversial and ranges from excision only, to excision with radiation therapy, to mastectomy. Prospective randomized trials reveal an approximate 50% reduction in local recurrence rate overall with the addition of radiation therapy to excisional surgery, but the published prospective data do not allow the selection of subgroups in whom the benefit from radiation therapy is so small that its risks outweigh its benefits. Nonrandomized single facility series suggest that age, family history, nuclear grade, comedo-type necrosis, tumor size and margin width are all important factors in predicting local recurrence and that one or more of these factors could be used to select subgroups of patients who do not benefit sufficiently from radiation therapy to merit its use. When all patients with ductal carcinoma in situ are considered, the overall mortality from breast cancer is extremely low, only about 1-2%. When conservative treatment fails, approximately 50% of all local recurrences are invasive breast cancer. In spite of this, the mortality rate following invasive local recurrence is relatively low, about 12% with eight years of actuarial follow-up. Genetic changes routinely precede morphological evidence of malignant transformation. Lessons learned from ongoing basic science research will help us to identify those DCIS lesions that are unlikely to progress and to prevent progression in the rest.