Ductal Carcinoma
In Situ
341
to vacuolated or clear. There is variable nuclear pleomor-
phism, sometimes manifested by prominent nucleoli.
A more complete discussion of apocrine carcinoma can be
found in Chapter 19.
Clear cell DCIS
is a poorly defined variant typically en-
countered with solid and comedo patterns (Fig. 11.7). Some
clear cell DCIS are composed of cells with an arrangement
described as “mosaic” because of the appearance created by
sharply defined cell borders (Fig. 11.7). A subset of lesions
classified under this heading includes forms of apocrine car-
cinoma. The presence of a monomorphic clear cell popu-
lation is highly suggestive of DCIS. Occasionally, clear cell
DCIS are strongly mucicarmine positive. Other clear cell le-
sions are probably the
in situ
form of lipid-rich or glycogen-
rich carcinomas discussed in separate chapters.
Spindle cell
DCIS may express neuroendocrine markers
such as chromogranin, synaptophysin, and neuron-specific
enolase.
111,112
The swirling growth pattern of cells in spindle
cell DCIS mimics “streaming,” which is characteristically
found in usual duct hyperplasia. Spindle cell DCIS often co-
exists with cribriform DCIS.
Small cell
DCIS is extremely uncommon. The growth pat-
terns are typically cribriform and solid or a mixture of these
forms. When present by itself, the solid pattern of small cell
DCIS can be distinguished from LCIS with the E-cadherin
immunostain that demonstrates membrane reactivity in
DCIS. E-cadherin staining is absent or fragmented and weak
in LCIS. “Neuroendocrine” DCIS is a less aggressive vari-
ant of small cell carcinoma (SCC) that is typically charac-
terized by solid growth and spindle cell with fine granular
cytoplasm, immunoreactivity for neuroendocrine markers,
and a lower proliferation rate than SCC.
112
The cellular composition of DCIS is typically
mono-
morphic
. This term has been applied especially to cribri-
form, solid, and micropapillary carcinomas. In this context,
monomorphic means that there is overall homogeneity in
the cytologic appearance of the DCIS cells—although there
may be minor variation among cells in terms of amount of
cytoplasm, nuclear size, etc. Variability in these parameters
derives in part from differences in the plane in which they
are sectioned. Cell and nuclear shape may be altered by the
presence or absence of crowding in one or another part of
the duct. The presence of a myoepithelial cell layer is not
a consideration in judging whether a ductal proliferation is
monomorphic.
Dimorphic variants of DCIS consisting of two distinctly
different populations of cells are unusual. The majority of
dimorphic DCIS are papillary carcinomas (see Chapter 14).
A dimorphic papillary DCIS with a small invasive compo-
nent of mucinous carcinoma is illustrated in Figure 11.8.
DCIS exhibits considerable tumoral heterogeneity,
and in a given patient can have more than a single mi-
croscopic structural, cytologic, or immunocytochemical
phenotype.
76,113,114
Mixed histologic patterns are found in
FIG. 11.6.
(Continued)
