Invasive breast carcinoma - IARC

A
B
Fig. 1.109 A Apocrine adenosis/sclerosing adenosis with apocrine metaplasia and focal atypia. B Immunostain for actin demonstrating myoepithelial cells around
the tubules. C Typical apocrine metaplasia in sclerosing adenosis, characterized by a three-fold nuclear size variation.
C
Apocrine adenosis
Synonym
Adenosis with apocrine metaplasia.
Apocrine adenosis (AA) is an ambiguous
term, as it has been used for several
diff e rent lesions {805,2698,2699}. In
this context, it is used for adenosis, particularly
sclerosing adenosis, with wides
p read apocrine metaplasia constituting
at least 50% of the adenotic are a
{3093}. The apocrine epithelium may
exhibit cytological atypia, so that the
histological appearance mimics invasive
carcinoma {2621,2698,2699}.
A
B
Fig. 1.110 A Nodular sclerosing adenosis. Note the
well delineated margins. B High power view of the
lesion in A, showing distorted and compressed
tubular structures and intervening hyaline stroma.
Such lesions may pose difficulties in the differential
diagnosis to invasive lobular carcinoma.
Blunt duct adenosis
The term blunt duct adenosis (BDA) has
been used for an organoid micro s c o p i c
f o rm of adenosis with variable distension
of lumens showing columnar cell
metaplasia {2015}.
Microglandular adenosis
M i c roglandular adenosis (MGA) is a
r a re lesion, characterized by a diff u s e
h a p h a z a rd proliferation of small ro u n d
glands {507,692,2413,2884}. These
may be clustered, but without sclero s i s
or compression {507,3081}. The surrounding
collagenous stroma may
be hypocellular or hyalinized. There is
no elastosis. The glands have a ro u n d
lumen, which frequently contains periodic
acid-Schiff (PAS) positive, eosinophilic
secre t o ry material. The epithelium
is cuboid and without snouts.
The cytoplasm may be clear or eosinophilic
and granular. There is no
nuclear atypia. There are no myoepithelial
cells {184,321,797,2884}, b u t
a surrounding basement membrane,
not always recognizable without
immunohistochemical staining for laminin
or collagen IV {692,2884, 3081},
is present. Electron microscopy shows
a multilayered basment membrane
s u r rounding the tubules of MGA
{ 2884 }.
The epithelium of MGA is positive for
S-100 in addition to cytokeratin {1372}.
When carcinoma arises in association
with MGA it may retain an alveolar patt
e rn {1331} or be of ductal or one of the
special types {2016}; the vast majority
of these invasive carcinomas retain
S-100 immunoreactivity re g a rdless of
their subtype {1484}.
Adenomyoepithelial adenosis
Adenomyoepithelial adenosis (AMEA)
is an extremely rare type of adenosis,
which seems to be associated with
adenomyoepithelioma {803,805,1454}
(see section on adenomyoepithelial
l e s i o n s ) .
Prognosis and predictive factors of
adenosis
Most types of adenosis are not associated
with increased risk of subsequent carcinoma.
However, there are exceptions,
as nearly one third of cases of MGA harbour
an invasive carcinoma {803,1454},
and apocrine adenosis has been found
to be monoclonal and perhaps a putative
precancerous lesion {3093}.
Radial scar /
Complex sclerosing lesion
Definition
A benign lesion that on imaging, gro s s l y
and at low power microscopy re s e m b l e s
invasive carcinoma because the lobular
a rc h i t e c t u re is distorted by the sclero s i n g
p rocess. The term radial scar (RS) has
b e en applied to small lesions and com-
Fig. 1.111 Blunt duct adenosis, typical morphology.
82 Tumours of the breast