Path Case- 44: Answer and Case Discussion:
Clear Cell Sarcoma of Tendons
(Malignant Melanoma of Soft Parts)
Path Quiz Online:Case-44: Case History and images:
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
diagnosis of clear cell sarcoma:
2. Malignant melanoma (mitotic activity ,cellular atypia and nuclear pleomorphism more prominent in melanoma) ;
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.
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