TABLE 2-2 Age Differences in DCIS Detected by Screening Mammography22

Age

Approximate Number of DCIS Cases Detected per Mammogram

Approximate Incidence of DCIS Cases Detected by Mammography

40-49

1 in 1800

0.06%

50-59

1 in 1500

0.07%

60-69

1 in 1000

0.1%

70-84

1 in 900

0.1%

cellular tissue underlying epithelial cells).40 The resulting disease ranges from low-grade lesions resembling atypical hyperplasia, to high-grade or anaplastic lesions. (Anaplastic lesions are made up of cells that have reverted to an immature or less differentiated form that is often indicative of invasive cancer.) The classification of different types of DCIS is described in Box 2-3.

The proliferation of epithelial cells in the lobules of the mammary ducts traditionally has been referred to as lobular carcinoma in situ (LCIS), but the current preferred term is lobular intraepithelial neoplasia (LIN), which includes both LCIS and atypical lobular hyperplasia.7 LIN and DCIS are neither invasive nor metastatic. In time, however, many DCIS lesions will become both invasive and metastatic.92 LIN, while an indicator of high risk for developing breast cancer, is not considered to be a pre-invasive cancer.106 It has no characteristic mammographic features and is typically detected by a biopsy performed for another reason,61 whereas the microcalcifications typical of many cases of DCIS are usually apparent on mammograms.

Only about 10 percent of mammographically detected DCIS will appear as a mass or asymmetry without calcifications; most DCIS is suspected on the basis of mammographic microcalcifications.22,71,109 This contrasts with invasive cancer, which usually appears as a mass or density on a mammogram. Mammograms frequently underestimate the extent of DCIS, particularly for larger lesions.41,42,43,71 Calcifications associated with DCIS vary in size, form and density, although they tend to be grouped in clusters, lines, or segmental arrangements that follow the morphology of the duct. Calcifications may also reflect the presence of benign conditions such as proliferative or nonproliferative fibrocystic change, although calcifications that result from these conditions are usually more rounded, more uniform in density, and more scattered in distribution than DCIS calcifications.71,88

A definitive diagnosis of DCIS requires pathologic evaluation of a biopsy specimen. To ensure complete accuracy of grading, a core or excisional biopsy must be performed.51 Stereotactic core biopsy is recommended and



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