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Soft Tissue Pathology 

Pathology of Clear Cell Sarcoma of Tendons and Aponeuroses

(Malignant Melanoma of Soft Parts)    

Dr Sampurna Roy MD       

Pathology Quiz Case 44: Case History and images  

Diagnosis: Clear Cell Sarcoma of Tendons and Aponeuroses  (Malignant Melanoma of Soft Parts)

 

                                                                                                                      

 

 

Clear cell sarcoma of tendons and aponeuroses is a rare aggressive, soft tissue sarcoma which was initially named malignant melanoma of soft parts.

It was originally described by Enzinger et al in 1965.

The tumour was called malignant melanoma of soft parts because it shows melanocytic differentiation.

Clear cell sarcoma stain positive for the melanocyte immunohistochemical markers HMB-45 and S-100. It is thought to derive from neural crest cells. These markers are useful for distinguishing clear cell sarcoma from epithelial tumours and synovial sarcomas.

It is a slow growing, progressive tumour with poor prognosis.

The tumour is commonly located in the extremities, specially around the knee, feet and ankle.

The patients are mostly young adults between the ages of 20 and 40 years with a higher incidence in female.

Grossly, the tumour is firm well circumscribed grey or white in appearance.

Microscopic features:

                           

S100 protein is strongly positive.   

Reticulin stain:   Nested architecture with loose meshwork of reticulin fibres , which  surround  the individual nests of tumour cells .

Microscopically, the tumour is characterized by solid nests and fascicles of tumour cells.  

The tumour cells are polygonal with clear cytoplasm or more spindle shaped with  pale eosinophilic cytoplasm.

Multinucleated giant cells (wreath-like nuclei) are present.

Junctional activity is absent and there is lack of pleomorphism.

The tumour infiltrates tendinous tissue, subcutis and even deep dermis.

Immunohistochemical analysis shows that the tumor cells are positive for vimentin, S-100, HMB45 and MelanA, and negative for AE1/AE3, actin,  desmin, CD117, TFE-3, and P63.

 

Poor prognosis is indicated by large size of the tumour , presence of necrosis and local recurrence. Tumors <5 cm are much less likely to recur or metastasize, whereas those >5 cm are more commonly associated with metastatic disease.Focal or diffuse tumor necrosis also correlates with a worse prognosis, independent of tumor size                       
Metastasis occurs in more than 50% cases.
Lymph node metastasis is  associated with a poor prognosis, since patients with regional metastasis eventually will develop distant metastasis. Common sites of metastasis include bone, lymphnode and lungs. Repeated local recurrence is common in clear cell sarcoma.

The characteristic translocation t (12 ; 22) (q13 ; q12)  results in a fusion gene EWS/ATF1.  

The EWS/ATF1 fusion transcript is detectable in almost 90% of cases.

 Differential diagnosis of clear cell sarcoma:

1. Malignant melanoma (mitotic activity, cellular atypia and nuclear pleomorphism more prominent in melanoma) ; It has been suggested that CD117 immunoreactivity, which was positive in metastatic melanoma, but not in clear cell sarcoma, may be useful for differentiation of these tumours. Clear cell sarcoma of the temporal region: case report, review of the literature, and genetic analysis. J Oral Maxillofac Surg. 2009;67:9104.

2. PEComas- Clear cell myomelanocytic tumour                                                     

3. Malignant peripheral nerve sheath tumour 

4. Melanotic Schwannoma,

5. Cellular Blue Naevus

6. Synovial Sarcoma (monophasic type),

7. Alveolar Soft Part Sarcoma

8. Epithelioid Sarcoma

 

Further reading:

Clinicopathological features, diagnosis and treatment of clear cell sarcoma/melanoma of soft parts.

Cutaneous clear cell sarcoma: a rare aggressive tumor with potential diagnostic challenge.

Clear cell sarcoma of soft tissue in right parapharyngeal region: report of a rare case.

Clear cell sarcoma: an institutional review.  

Clear cell sarcoma of soft tissues.

Clear-cell sarcoma diagnosis by fine needle aspiration: cytologic,histologic and ultrastructural features; potential pitfalls;and literature review.

Molecular diagnosis of clear cell sarcoma: EWS-ATF1 and MITF-M transcripts and histopathological and ultrastructural analysis of 12 cases. 

Newly established clear cell sarcoma (malignant melanoma of soft parts) cell line expressing melanoma associated Melan A antigen and overexpressing c-myc gene.

Clear cell sarcoma of tendons and aponeuroses: A review.  

Clear cell sarcoma (malignant melanoma) of soft parts: A clinicopathologic study of 30 cases. 

Malignant melanoma of soft parts (clear cell sarcoma). A study of 17 cases, with emphasis on prognostic factors.

Clear cell sarcoma of tendons and aponeuroses: An analysis of 21 cases.

 

 

 

Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)


 

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