Ductal carcinomain situ (DCIS) is a noninvasive condition. DCIS can progress to become invasive cancer, but estimates of the likelihood of this vary widely. Some people include DCIS in breast cancer statistics. The frequency of the diagnosis of DCIS has increased markedly in the United States since the widespread use of screening mammography. In 1998, DCIS accounted for about 18% of all newly diagnosed invasive plus noninvasive breast tumors in the United States.
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Very few cases of DCIS present as a palpable mass; 80% are diagnosed by mammography alone. DCIS comprises a heterogeneous group of histopathologic lesions that have been classified into several subtypes based primarily on architectural pattern: micropapillary, papillary, solid, cribriform, and comedo. Comedo-type DCIS consists of cells that appear cytologically malignant, with the presence of high-grade nuclei, pleomorphism, and abundant central luminal necrosis. Comedo-type DCIS appears to be more aggressive, with a higher probability of associated invasive ductal carcinoma.
Treatment Option Overview
Until recently, the customary treatment of DCIS was mastectomy. The rationale for mastectomy included a 30% incidence of multicentric disease, a 40% prevalence of residual tumor at mastectomy following wide excision alone, and a 25% to 50% incidence of breast recurrence following limited surgery for palpable tumor, with 50% of those recurrences being invasive carcinoma.[1,3] The combined local and distant recurrence rate following mastectomy is 1% to 2%. No randomized comparisons of mastectomy versus breast-conserving surgery plus breast radiation are available.
In view of the success of breast-conserving surgery combined with breast radiation for invasive carcinoma, this conservative approach was extended to the noninvasive entity. To determine whether breast-conserving surgery plus radiation therapy was a reasonable approach to the management of DCIS, the National Surgical Adjuvant Breast and Bowel Project (NSABP) and the European Organisation for Research and Treatment of Cancer (EORTC) have each completed prospective randomized trials in which women with localized DCIS and negative surgical margins following excisional biopsy were randomized to either breast radiation (50 Gy) or to no further therapy.[4,5,6,7]
Of the 818 women enrolled in the NSABP-B-17 trial, 80% were diagnosed by mammography, and 70% of the patients' lesions were 1 cm or less. At the 12-year actuarial follow-up interval, the overall rate of in-breast tumor recurrence was reduced from 31.7% to 15.7% when radiation therapy was delivered (P < .005). Radiation therapy reduced the occurrence of invasive cancer from 16.8% to 7.7% (P = .001) and recurrent DCIS from 14.6% to 8.0% (P = .001).[Level of evidence: 1iiDii] Nine pathologic features were evaluated for their ability to predict for in-breast recurrence, but only comedo necrosis was determined to be a significant predictor for recurrence.