Ductal Carcinoma
In Situ
349
adenoid cystic carcinoma (AdCC) or a complex papilloma.
Collagenous spherulosis that is usually associated with hy-
perplastic duct lesions can, in rare instances, be involved by
DCIS (Fig. 11.20). The resultant structure resembles cribri-
formDCIS because the spherules simulatemicrolumens. The
presence of collagenous spherulosis can be confirmed with
either heavy-chain myosin or SMA immunostain, which will
highlight myoepithelial cells at the perimeter of spherules or
immunostains for basement membrane components (such
as laminin or collagen IV). LCIS can also inhabit collagenous
spherulosis. The distinction between intraductal and
in situ
lobular carcinoma in collagenous spherulosis depends on
cytologic features of the lesion and can be confirmed with
the E-cadherin or p120 immunostains. The appearance of
any adjacent coexisting
in situ
carcinoma not in collagenous
spherulosis can also be helpful.
The secondary microlumina in cribriform DCIS tend to
be round or oval, with smooth luminal edges bordered by cu-
boidal cells (Fig. 11.21). The distribution of microlumina is
variable. In some instances, the spaces are spread across the
entire duct or concentrated toward the center. The presence
of microlumina entirely at the periphery of the duct is usu-
ally an indication of hyperplasia, but this appearance may
be mimicked in cribriform DCIS when the center of the
duct is destroyed by necrosis (Fig. 11.22). It is a hallmark of
cribriform DCIS that the microlumina be surrounded by a
homogeneous cell population that is uniformly distributed
throughout the duct. The microlumina may contain secre-
tion, small numbers of degenerated or necrotic cells, and
punctate calcifications.
Bands of neoplastic cells between and around the mi-
crolumina in cribriform DCIS are described as “rigid,” a
term that refers to the uniform, nonoverlapping, distribu-
tion of polygonal cells in contrast to the streaming pattern
of overlapping, frequently oval cells in duct hyperplasia
(Fig. 11.23). Polarization of the cells in an orderly fashion
around the microlumina contributes to the “rigid” appear-
ance. The most orderly type of cribriform DCIS is composed
of cuboidal to low columnar monomorphic cells with low
nuclear grade. Nucleoli are inconspicuous or absent, and
mitoses are rarely encountered. The cells usually have sparse
cytoplasm. An apocrine variant is composed of cells with
low- to intermediate-grade nuclei and more abundant gran-
ular eosinophilic cytoplasm (Fig. 11.24). Secretion is found
in some but not all cribriform microlumina, and when pres-
ent it can form small calcifications. Cribriform DCIS with
necrosis, mitotic activity, and poorly differentiated nuclear
grade is rare, and these lesions tend to have less well-defined
microlumina (Fig. 11.25). The cribriform pattern of carci-
noma may either represent DCIS or invasive carcinoma. The
latter disease is an uncommon entity that is characterized by
an infiltrative pattern of growth (Chapter 26).
In some circumstances, it may be difficult to distinguish
between cribriform and other structural subtypes of DCIS,
and in these instances the choice is sometimes arbitrary.
Fibrovascular stroma and myoepithelial cells are not present
in the epithelium of cribriform DCIS, but myoepithelial cells
may persist at the periphery of the involved duct (Fig. 11.4).
Solid papillary DCIS in which fibrovascular stroma is clearly
evident occasionally has a prominent fenestrated pattern
that mimics cribriform DCIS. The stromal component of
FIG. 11.17.
DCIS with squamous metaplasia.
A:
Isolated foci of squamous metaplasia are present
in the micropapillary carcinomatous epithelium (
arrow
).
B:
Squamous metaplasia in solid DCIS.
FIG. 11.18.
DCIS, micropapillary clear cell type.
