Invasive breast carcinoma - IARC

A
B
Fig. 1.128 Adenomyoepithelioma, spindle cell type. A There is a solid proliferation of spindled myoepithelial cells surrounding irregular epithelial lined spaces. B The epithelial
spaces may show apocrine metaplasia. C Immunostain for S-100 protein shows positivity in the proliferating myoepithelial cells, while the epithelial cells fail to react.
C
Adenomyoepithelial adenosis
Definition
An extremely rare type of adenosis associated
with adenomyoepithelioma {803,
805,1454}.
Histopathology
Adenomyoepithelial adenosis (AMEA)
consists of a diffuse proliferation of
round or irregular tubular structure s
lined by a cuboidal to columnar epithelium,
which may show apocrine metaplasia.
There is a prominent, focally hyperplastic
myoepithelial cell layer with strikingly
clear cytoplasm. There is no significant
nuclear atypia or mitotic a c t i v i t y,
but most described cases blend with
or surround an adenomyoepithelioma
{803,805,1454}.
Adenomyoepithelioma
Definition
Composed of a predominantly and usually
solid proliferation of phenotypically variable
myoepithelial cells around small epithelial
lined spaces, in rare instances, the
epithelial, the myoepithelial or both components
of an adenomyoepithelioma (AME)
may become malignant (malignant AME).
A
ICD-O codes
Benign 8983/0
Malignant 8983/3
Macroscopy
Well delineated, benign adenomyoepitheliomas
are rounded nodules with a
median size of 2.5 cm.
Histopathology
Histologically, AMEs they are characterized
by a proliferation of layers or
sheaths of ME cells around epithelial
lined spaces. The tumour may display a
spindle cell, a tubular, or, most often, a
lobulated growth pattern. Fibrous septae
with central hyalinization or infarction are
common in the lobulated lesions. The ME
cell phenotype is most variable in the
lobulated pattern ranging from clear to
eosinophilic and hyaline (plasmacytoid)
types. Satellite nodules, seen adjacent to
the lobulated variant in some cases
reflect an intraductal extension of the
lesion. The tubular variant has an ill
defined margin. Mitotic activity of the
proliferating myoepithelial cells in benign
lesions is generally in the range of 1-
2/10, always ≤2/10 high power field (hpf).
Either the epithelial, the myoepithelial or
both components of an adenomyoepithelioma
may become malignant and
Fig. 1.129 Adenomyoepithelioma, adenosis type. A At least focally well delineated, these tumours superficially
resemble a tubular adenoma. B Higher magnification shows proliferation of ME cells in the tubules
beyond the normal single layer.
B
give rise to a carcinoma while the backg
round lesion retains its adenomyoepitheliomatous
appearance {793,900,903,
1695,2868,2953}. The aggressive myoepithelial
component may assume a spindle
configuration and develop into nodules
resembling myofibroblastic lesions.
A variety of epithelial derived carc i n o-
mas, sarcomas and carc i n o s a rc o m a s
occur in this setting (Table1.16) {2868}.
R a re l y, both components develop into
either separate malignancies or a single
malignant infiltrative process composed
of angulated tubules lined by both
epithelial and myoepithelial cells.
Differential diagnosis
The tubular variant of AME should be
distinguished from a tubular adenoma;
the latter may have prominent ME cells,
but lacks the myoepithelial pro l i f e r a t i o n
typical of an AME. Furt h e rm o re, tubular
adenoma is sharply circumscribed unlike
the ill defined tubular AME.
The lobulated and spindle cell variants
of AME should be distinguished fro m
Table 1.16
Classification of myoepithelial lesions.
1 .M y o e p i t h e l i o s i s
a. Intraductal
b. Periductal
2 . Adenomyoepithelial adenosis
3 .A d e n o m y o e p i t h e l i o m a
a .B e n i g n
b . With malignant change (specify the subtype)
– Myoepithelial carcinoma arising in an aden
o m y o e p i t h e l i o m a
– Epithelial carcinoma arising in an adenomyo
e p i t h e l i o m a
– Malignant epithelial and myoepithelial comp
o n e n t s
– Sarcoma arising in adenomyoepithelioma
– Carcinosarcoma arising in adenomyoepithelioma
4. Malignant myoepithelioma (ME carcinoma)
Myoepithelial lesions
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