346
Chapter 11
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).
A
C
E
D
B
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
