Path Case- 44: Answer and Case Discussion:

              Clear Cell Sarcoma of Tendons

                       and Aponeuroses

            (Malignant Melanoma of Soft Parts)

               Dr  Sampurna Roy  MD

     Path Quiz Online:Case-44: Case History and images:

                          
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.

Microscopically, the tumour is characterized by solid nests and fascicles of tumour cells.   Image Link1 ; Image Link2 ; Image Link3 ; Image Link4 ; Image Link5.

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.
                   

              IMAGE LINKS: Clear cell sarcoma- (ESCOP)
                      Link1  ; Link2  ; Link3 ; Link4 ; Link5

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   ;

                                   
                          
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.

    Visit:  Clear cell 'sugar" Tumour of Lung  ; Lymphangioleiomyomatosis

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
                     Abstract1   ;Abstract2 ; Abstract3  ; Abstract4