Invasive breast carcinoma - IARC

Myoepithelial lesions
F.A. Tavassoli
J. Soares
Definition
Lesions either derived from, or composed
of, a dominant to pure population
of myoepithelial (ME) cells. They include
adenoid cystic carcinoma, pleomorphic
adenoma, myoepitheliosis, adenomyoepithelial
adenosis, adenomyoepithelioma
(benign or malignant) and malignant
myoepithelioma (myoepithelial carcinoma).
The first two lesions are discussed
elsewhere. In this section, the
focus will be on the others.
H i s t o p a t h o l o g y
The intraductal proliferating spindle
cells may develop a prominent palisading
pattern. The cuboidal cells may
have longitudinal nuclear grooves resembling
transitional cells. Rarely atypia
and mitotic activity appear, warranting a
designation of atypical myoepitheliosis.
The periductal variant of myoepitheliosis
is often associated with sclero s i s
and is considered by some to be a
variant of sclerosing adenosis; the cells
have varied phenotypes.
When completely excised, re c u r re n c e s
do not develop.
Immunohistochemical profile of
myoepithelial cells
Myoepithelial cells show positive immun
o reaction with alpha smooth muscle
actin, calponin, caldesmon, smooth muscle
myosin heavy chain (SMM-HC)
maspin S-100 protein and high MW
cytokeratins 34betaE12, CK5 and CK14.
Nuclear immunoreactivity with p63 is also
a feature of ME cells. Rarely there is
staining with glial fibrillary acidic protein
(GFAP). Myoepithelial cells are negative
for low MW cytokeratins (CK 8/18), estrogen
receptor (ER), progesterone receptor
(PR), and desmin {191,1516,1573,
1741,2418,2702,2738,2953,3099}.
A
Fig. 1.125 Myoepitheliosis, periductal type. A The myoepithelial cells with abundant eosinophilic cytoplasm
proliferate around the epithelial cells compressing the ductular lumens. This change is often multifocal.
B Immunostain for actin is positive in the myoepithelial cells, but negative in the epithelial-lined compressed
ductular spaces.
B
Epidemiology
Patients range in age from 22 to 87 years
{2418,2868,2875,3192}.
Clinical features
A p a rt from myoepitheliosis, which is rare l y
palpable, these lesions usually present as
a palpable tumour and/or mammographic
density without distinctive feature s .
A
Fig. 1.126 Adenomyoepithelial adenosis. A Prominent clear m y o e p i t h e l i a l (ME) cells are evident around
several ductules. B Both the clear and normal ME cells are intensely imunoreactive for S-100 protein.
B
Myoepitheliosis
Definition
A multifocal, often microscopic, proliferation
of spindle to cuboidal myoepithelial
cells growing into and/or around small
ducts and ductules.
Macroscopy
Myoepitheliosis generally appears as a
firm irregular area.
A
Fig. 1.127 Adenomyoepithelioma, lobulated type. A The lobulated nature of the tumour is apparent with massive
central infarction in the two adjacent nodules. The lighter cells reflect the proliferating ME cells, while
the darker cells represent the epithelial cells. B Adenomyoepithelioma. In this case, the proliferating ME
cells have a clear cell phenotype and surround a few spaces lined by darker epithelial cells.
B
86 Tumours of the breast