Rosen's Breast Pathology, 4e

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Chapter 11

A

B

D

C

FIG. 11.12.  DCIS, micropapillary. A,B: Mixed flat and micro- papillary carcinoma. C: Micropapillary fronds and central necrosis are shown. D,E: Arcuate micropapillary fronds ex- tend into duct lumens. Dense calcific deposits are present in (E).

E

micropapillary DCIS is more likely to have calcifications than the low-grade variant, and necrotic cellular debris may be found in the duct lumen. In an interinstitutional study, it was found that high nu- clear grade micropapillary DCIS more frequently overex- pressed HER2, had a higher proliferation index, displayed necrosis and microinvasion, and was more extensive than those of low- and intermediate-grade nuclei. 117 Further- more, in the same series, high nuclear grade was found to be the only parameter associated with elevated risk of local recurrence after breast-conserving surgery for ­micropapillary DCIS.

Two subtypes of micropapillary carcinoma have been given specific designations. Cystic hypersecretory DCIS is discussed in Chapter 24. The term flat micropapillary carci- noma (so-called “clinging” carcinoma) refers to DCIS with the cytologic appearance of the micropapillary lesion that is lacking in fully developed epithelial fronds (Fig. 11.11). Lesions composed entirely of flat micropapillary DCIS are very uncommon, and more often one or more epithelial fronds or bridges are present. In the absence of calcification or necrosis, flat micropapillary DCIS is easily overlooked microscopically. This type of DCIS is most often found in a background of CCH, which is encountered mainly in