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Ewing sarcoma family
of tumours includes Ewing sarcoma, peripheral primitive neuroectodermal
tumor, neuroepithelioma, atypical Ewing sarcoma, and Askin tumour.
Case
Presentation(Complejo
Académico Hospitalario Nelson Mandela REPUBLICA SUDAFRICANA)
Peripheral
primitive neuroectodermal tumours are characterized by chromosomal
translocation t(11;22)(q24;q12) in almost 90% cases.
Ewing
sarcoma and the peripheral primitive neuroectodermal tumor were both found
to contain the same reciprocal translocation between chromosomes 11 and
22, t(11;22). Both lesions have
similar patterns of biochemical and oncogene expression.
Age:
The
tumour is common between 10 and 30 years.
Site:
Usually occurs in deep soft tissue and rarely involves
dermis and subcutis. The common sites include paravertebral and
intercostal regions as well as on the lower limbs. Rarely pelvic and hip
regions are involved.
Tumour located on the chest wall (may involve ribs, pleura and lung) is
referred to as Askin tumour.
Clinical presentation:
The tumour presents as a rapidly enlarging,
pale, soft mass with extensive necrosis. One third of the cases are
painful.
Microscopic features:
The tumour cells are
arranged in a trabecular or lobular growth pattern. A prominent vascular
network is present in the backround.
The microscopic features depends on
the degree of neuroectodermal differentiation.
Malignant primitive
neuroectodermal tumours (peripheral neuroepithelioma)- well differentiated
end of the spectrum.
The tumour cells show eosinophilic cytoplasm,coarse chromatin and
prominent nucleoli.
Homer Wright rosette containing central core of neurofibrillary material.
Flexner-Wintersteiner rosette containing central lumen.
PAS positivity is present in about 40% of cases. A peripheral
neuroepithelioma must demonstrate positivity with at least two neural
markers.
Extraskeletal Ewing's
sarcoma- poorly differentiated end of the spectrum. The tumour cells
show scanty, pale, cytoplasm, fine dusty chromatin and inconspicuous
nucleoli. The cells contain glycogen . PAS positivity is prominent.
Immunohistochemistry shows characteristic positivity with the neural
markers.
Immunohistochemistry:
The tumour
cells show diffuse membrane positivity positivity with
CD99 antigen (product of the
MIC2 gene) .
The tumour cells
are usually positive for neuron-specific enolase, PGP9.5, neurofilament ,
Leu-7 and synaptophysin.
Note: About 10% cases of PNET may demonstrate dot like positivity with
cytokeratin. PNET and Ewing's sarcoma are immunopositive to vimentin.
Differential diagnosis: (Small blue cell tumours):
Lymphoblastic lymphomas/leukaemia ; rhabdomyosarcoma
; mesenchymal chondrosarcoma ;
desmoplastic small round cell tumor ; synovial sarcomas, solitary fibrous
tumor ; extrarenal malignant rhabdoid tumour ; neuroendocrine tumors - may
demonstrate immunoreactivity to MIC-2.
The MIC-2 immunostain should
always be done in a panel, which usually includes muscle markers
(desmin, muscle-specific actin, myoD1, myogenin), neural markers
(protein gene product 9.5, S100 protein, neuron specific enolase, CD57,
synaptophysin, neurofilament protein), epithelial markers
(epithelial membrane antigen, cytokeratin), and lymphoid markers
(CD45, CD30, Tdt, T-cell and/or B-cell markers).
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Desmoplastic small
blue cell tumour: click
-
Poorly
differentiated synovial sarcoma: click
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Merkel
cell carcinoma: click
.
CK20 shows
dot positivity and EMA positivity.
-Neuroblastoma - CD99 negative.
-Solitary
fibrous tumor:click
-Extrarenal malignant rhabdoid tumour:click
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