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Chapter 11
FIG. 11.10.
DCIS.
A:
The smaller duct contains solid carcinoma with low nuclear grade and the
larger duct contains cribriform carcinoma with necrosis and high nuclear grade.
B:
The duct on
left contains solid DCIS with intermediate-grade nuclei, and the duct on the
right
shows cribriform
DCIS with relatively higher grade nuclei and calcification.
A
B
structural patterns are considered subsequent to a discus-
sion of the current conventional structural classification.
Structural Classification of DCIS
Micropapillary
DCIS consists of ducts lined by a layer of
neoplastic cells giving rise at intervals to papillary fronds or
arcuate formations protruding into the duct lumen. When
micropapillae are inconspicuous or absent, this type of
DCIS has been described as flat or “clinging” because the
neoplastic epithelium seems to hug the basement membrane
(Fig. 11.11).
116
The papillae are variable in appearance, rang-
ing from short bumps or mounds to long slender processes
(Fig. 11.12). The papillae lack a fibrovascular core and are
composed of cytologically homogeneous carcinoma cells.
Lesions in which the carcinomatous epithelium is supported
by fibrovascular stroma should be classified as papillary
carcinomas, even if the growth pattern is predominantly
micropapillary (Fig. 11.13). Arcuate structures, commonly
referred to as Roman bridge (or aqueduct) arches, occur
when microlumens are formed under adjacent coalescent
fronds or within a mound of neoplastic cells. These fenes-
trations resemble the lumens formed in cribriform DCIS
(Fig. 11.14). In conjunction with micropapillae, these arches
are a feature of micropapillary DCIS and do not warrant a
diagnosis of cribriform DCIS. In some situations, the micro-
papillary and cribriform patterns merge (Fig. 11.15). Some
samples of micropapillary DCIS develop complex, frond-
forming structures without evolving into cribriform growth
(Fig. 11.16).
The appearance of the micropapillary fronds varies
somewhat with the plane of individual histologic sections.
Whereas some micropapillae are cut perpendicular to their
long axis, others are seen sectioned tangentially or trans-
versely, resulting in irregular nests of seemingly detached
cell clusters in the duct lumen (Fig. 11.16). Ducts with low
nuclear grade micropapillary DCIS are usually relatively free
of cellular debris or inflammatory cells. Calcifications that
are granular, crystalline, or laminated occur particularly
when carcinoma arises in a background of columnar cell hy-
perplasia (CCH) (Fig. 11.11).
In micropapillary DCIS, the normal epithelial layer of the
duct is replaced by a single population of neoplastic cells.
In any given case, the appearance of the carcinoma cells is
relatively homogeneous, but cytologic heterogeneity can
occur between individual cases. Most often, micropapillary
DCIS is composed of cytologically low-grade homogeneous
cells with a high nuclear-to-cytoplasmic ratio and dense,
hyperchromatic nuclei (Figs. 11.12, 11.14, and 11.15). The
nuclei typically vary little in size, and chromatin density is
consistent between cells at the base and tip of micropapil-
lae. Nuclei may be slightly smaller and darker at the surface,
but marked disparity in these characteristics is a feature of
micropapillary hyperplasia (see Chapter 9). At the margin
of the duct, between papillary and arcuate structures, the
neoplastic cells are typically arranged in a layer that rarely
exceeds three cells in depth. The nuclei of the cells in the
epithelium between micropapillae are usually unevenly dis-
tributed in relation to the basement membrane (Figs. 11.12,
11.14, and 11.16). Persistent nonneoplastic epithelium be-
tween micropapillae is a feature of micropapillary hyper-
plasia rather than of micropapillary carcinoma. Mitoses are
rarely present in low-grade micropapillary DCIS. The carci-
noma cells tend to be so crowded and overlapping that their
individual borders and cytoplasm cannot be identified. Oc-
casionally, the cells have slightly more abundant cytoplasm,
with apocrine-type protrusions at the luminal border. In
one variant of this cell type, the nuclei of the tumor cells
are contained in cytoplasmic blebs that are extruded into
the duct lumen. Low-grade micropapillary DCIS can be
found near some tubular carcinomas. These patients often
have multifocal CCH with atypia and may also have LCIS
