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Pathology of Clear Cell Sarcoma of Tendons and Aponeuroses

(Malignant Melanoma of Soft Parts)               

Pathology Quiz Case 44: Case History and images  

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

 December 2015

Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)


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Aggressive Angiomyxoma

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Myxoid Tumours of Soft Tissue

Classification of Soft Tissue Tumour

Gross examination of soft tissue specimen          

A practical approach to histopathological reporting of soft tissue tumours

Grading of soft tissue tumours

Lipomatous tumours

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Notochordal Tumour - Chordoma

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Kaposi's sarcoma

Epithelioid hemangioendothelioma

Clear cell sarcoma of tendons and aponeuroses (also known as malignant melanoma of soft parts) is a slow and 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.

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.

Tumour cells contain melanin which is demonstrated by S100 protein, HMB45 and micropthalmia transcription factor. 

NSE , vimentin and keratin are also demonstrated by the tumour cells.

Poor prognosis is indicated by  large size of the tumour , presence of necrosis and local recurrence.                          

Metastasis occurs in more than 50% cases. 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 ; q13)  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. PEComas- Clear cell myomelanocytic tumour                                                     

2. Malignant melanoma (mitotic activity, cellular atypia and nuclear pleomorphism more prominent in melanoma) ;

3. Malignant peripheral nerve sheath tumour  ;


Pathology of Clear Cell Myomelanocytic Tumour: (PEComa)

Read: Malignant perivascular epithelioid cell tumor (PEComa)

“Malignant” Perivascular Epithelioid Cell Neoplasm

Clear cell myomelanocytic tumour (CCMMT) belongs to the perivascular epithelioid cell family of tumours (PEComa).

The tumours are usually located in or adjacent to the falciform ligament/ligamentum teres.

These tumours are common in children and young adults. One case has been reported in the urinary bladder.

Other PEComas includes angiomyolipoma (renal and extrarenal) , lymphangioleiomyoma, and clear cell 'sugar' tumours of pancreas, uterus and lungs.

PEComas are often associated with patients having tuberous sclerosis. 

Both benign and malignant tumours have been described.

Malignant tumours are diagnosed by histologically confirmed lymph node metastases and radiological evidence of pulmonary metastases.

Histopathological features:  These tumours are closely located to vascular structures and are characterized by  spindle to epithelioid cells with clear to pale eosinophilic cytoplasm arranged in fascicular or nested patterns.

Immunohistochemically, the tumour cells expressed HMB45 and smooth muscle actin and micropthalmia transcription factor. 

In some cases Melan A is positive. 

S100 protein and desmin are negative. Case link  


Further reading:

Clear cell myomelanocytic tumor of the thigh: report of a unique case.

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. 

Cytologic features of clear cell sarcoma (malignant melanoma)of soft parts a study of fine-needle aspirates and exfoliative specimens. 

Clear cell sarcoma arising in the retroperitoneum.

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

Diagnostic utility of micropthalmia transcription factor in malignant melanoma and other tumours.  

Clear cell sarcoma shows immunoreactivity for micropthalmia transcription factor: further evidence for melanocytic differentiation.  

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.  

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