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Chapter 11

CK5/6 positive) in 8% of DCIS and found it to be associ- ated with unfavorable prognostic variables, including high- grade nuclei, p53 overexpression, and elevated proliferation index. 202 Basal-like DCIS using the immunohistochemical profile of (triple negative, CK5/6 positive and EGFR positive as a surrogate for gene expression profiling) has been shown to have a doubled, yet statistically insignificant, risk of local recurrence and developing invasive cancer compared with other types. In this study of 392 patients, 32 (8.2%) were basal-like. 244 No significant difference has been detected in the ampli- fication of certain key genes, including ESR1 that encodes for ER, CCND1 that encodes for cyclin D1, and MYC that encodes for a helix-loop-helix/leucine zipper protein, be- tween DCIS and invasive breast carcinoma. 245 This indicates that these genes are implicated in cancer development but, perhaps, not in the initiation of invasive carcinoma. Needle Core Biopsy FS examination is not appropriate for a needle core biopsy of a nonpalpable mammographically detected lesion, unless there are exceptional circumstances. 246 Grading of DCIS in paraffin sections of needle core biopsies is generally accu- rate, but the probability of structural variability increases with the size of the lesion. Calcifications and necrotic debris may become dislodged in a needle core biopsy specimen, and rarely this material is the only component of DCIS in the sample (Fig. 11.60). In this circumstance, serial sections should be prepared. An ex- cisional biopsy should be considered, even if no epithelial el- ements of carcinoma are detected in serial sections that show displaced calcification of a type (i.e., amid ghost cells and karyorrhectic debris) that might occur in DCIS. A dislodged fragment of DCIS that becomes embedded in fat or stroma as part of a needle core biopsy sample may be mistaken for invasive carcinoma (Fig. 11.61).

“Healed” DCIS and end-stage periductal mastitis can both result in indistinguishable scarred ductal structures with calcifications (Fig. 11.62). When this type of structure is found in a needle core biopsy specimen, multiple serial sections should be prepared to search for scant foci of carci- noma that may be present. The limited epithelial abnormali- ties found in some of these cases may result in a diagnosis of ADH. A surgical excision is indicated for the latter diagnosis and in some situations may be appropriate when ductal scars are present without epithelial atypia if the mammographic findings raise concern about carcinoma. The distinction between invasive carcinoma and SA or radial sclerosing lesions can be challenging in needle core bi- opsy specimens. This difficulty is compounded when DCIS arises in sclerosing lesions (Fig. 11.63). It is important to consider this potential diagnostic pitfall and to employ im- munohistochemical stains to define the distribution of myo- epithelial cells in the specimen. Incomplete samples of radial sclerosing lesions obtained in needle core biopsy samples are difficult to assess for intraductal or invasive carcinoma, and they may be reported as atypical hyperplasia. A needle core biopsy specimen cannot be relied upon to measure the size of a DCIS lesion, even if the procedure is performed for calcifications alone and calcifications are no longer present in a follow-up mammogram. The needle bi- opsy specimen rarely provides a single intact sample of the lesion, and it is not feasible to reassemble the DCIS foci from multiple samples to obtain a single measurement. The diagnosis of DCIS in a needle core biopsy speci- men does not exclude the possibility of invasive carcinoma in the affected breast. The reported frequency of invasive carcinoma detected in excisional biopsies performed after a needle core biopsy diagnosis of DCIS was 15% to 27%. 247–253 The diagnosis of DCIS without invasion was reported to be more reliable with directional vacuum-assisted biopsy pro- cedure than with the automated needle biopsy system. 249 The diagnosis of DCIS on needle core biopsies can in- fluence the extent of the subsequent surgery. Dillon et al. 254

FIG. 11.60.  DCIS, needle core biopsy. A: Fragmented calcification surrounded by necrotic debris and sparse isolated atypical cells in blood were the significant findings in a needle core biopsy specimen. B: Subsequent surgical excision revealed micropapillary DCIS with calcifications.