Invasive breast carcinoma - IARC

Table 1.17
Immunoprofile of various spindle cell tumours of the breast.
Tumour Smooth muscle Calponin S-100 Kermix* CAM5.2** ER Desmin CD34 HMB45
a c t i n
Myoepithelioma + + + + – – – – –
Spindle cell carcinoma – – – ++ + +/– – – –
Smooth muscle cell tumours + +/– – +/– +/– +/– + – –
Myofibroblastic lesions + +/– +/– – – – –* + –
Melanoma – – + – – – – – –
________
* Kermix a cocktail of AE1/AE3 (cytokeratin 1-19), and LP34 (CK5,6 & 18)
**Cam 5.2 (CK8 & 18)
pleomorphic adenoma; the latter generally
has prominent areas of chondro i d
and/or osseous diff e re n t i a t i o n .
Prognosis and predictive factors
The majority of AME are benign {1573,
1695,2418,2581,2868}. Lesions that
contain malignant areas, those with
high mitotic rate, or infiltrating margins
have a potential for re c u r rence and
metastases. Local re c u r rence {1440,
2868,3192} as well as distant metastasis
{2875} have been described, mainly
among those with agressive features.
significant atypia. Mitotic activity may
not exceed 3-4 mf/10hpf. The spindled
tumour cells appear to emanate fro m
the myoepithelial cells of ductules
entrapped in the periphery of the lesion.
A g g regates of collagen and pro m i n e n t
central hyalinization may be evident.
Differential diagnosis
The diff e rential diagnosis includes spindle
cell carcinomas, fibromatosis and a
variety of myofibroblastic lesions. The
p resence of a dominant nodule with
i r regular and shallow infiltration at the
margins is helpful in distinguishing this
lesion from fibromatosis and myofibro b-
lastic tumours. Immunohistochemistry
is, and, rare l y, electron microscopy may
be, re q u i red to confirm the myoepithelial
n a t u re of the neoplastic cells.
Prognosis and predictive factors
Local recurrence or distant metastases
have rarely been documented {1573,
2581,2875}. Complete excision with uninvolved
margins is recommended.
Malignant myoepithelioma
Definition
An infiltrating tumour composed purely of
myoepithelial cells (predominantly spindled)
with identifiable mitotic activity.
Synonyms
Infiltrating myoepithelioma, myoepithelial
carcinoma.
ICD-O code 8982/3
Macroscopy
Ranging from 1.0 to 21 cm in size, these
tumours are generally well defined with
focal marginal irre g u l a r i t y, although
some are stellate. There may be foci of
n e c rosis and haemorrhage on the firm
r u b b e ry cut surface in larger tumours
and sometimes nodular areas of hyalinization
even in smaller tumours.
Histopathology
H i s t o l o g i c a l l y, there is an infiltrating proliferation
of spindle cells often lacking
A
Fig. 1.130 Malignant myoepithelioma (myoepithelial carcinoma). A The lesion is composed of spindle cells
lacking significant atypia or mitotic activity. B At the periphery of the same lesion, often a more epithelioid
or plump cell population is evident emanating from the myoepithelial cell layer of the entrapped ductules.
A
Fig. 1.131 Malignant myoepithelioma. A Immunostain for smooth muscle actin is positive in the neoplastic spindle
cells. B Immunostain for kermix (AE1/AE3/LP34) shows intense staining of the entrapped normal ductules; a
less intense immunoreaction is evident in the neoplastic spindle cells.
B
B
88 Tumours of the breast