Clear Cell Sarcoma



Clear Cell Sarcoma


Elizabeth A. Montgomery, MD









Hematoxylin & eosin shows a lobulated (“packeted”) appearance of nests of neoplastic cells in a tendon or aponeurosis.






Hematoxylin & eosin shows monotonous cells, each with a uniform enlarged nucleus. A wreath-like tumor giant cell image is present in the center of the field.


TERMINOLOGY


Abbreviations



  • Clear cell sarcoma (CCS)


Synonyms



  • Malignant melanoma of soft parts


Definitions



  • Sarcoma showing melanocytic differentiation



    • Different from clear cell sarcoma of kidney


CLINICAL ISSUES


Epidemiology



  • Incidence



    • Rare


  • Age



    • Young adults (3rd or 4th decade)


  • Gender



    • Slight female predominance


Presentation



  • Painless mass


  • Usually affects extremities (> 90%)



    • Foot most common site


  • Often attached to tendon or aponeurosis


  • No associated skin lesions



    • Important in separating CCS from melanoma


  • Occasional visceral examples



    • GI tract most common visceral site



      • Ileum most common GI site


Prognosis



  • Behaves as high-grade sarcoma



    • 5-year survival (50-65%)


  • Metastasizes to lymph nodes and lung


  • Differs from behavior of melanoma despite overlapping features



    • For example, 1 cm clear cell sarcoma may have good prognosis while 1 cm melanoma likely to be lethal


    • Metastatic pattern that of sarcoma


MACROSCOPIC FEATURES


Size



  • 2-6 cm; median size: 2.5-3.5 cm


  • Lobulated gray-white masses


MICROSCOPIC PATHOLOGY


Histologic Features



  • Monotonous clear to spindled cells arranged in nests/packets usually infiltrating tendon sheath



    • Abundant glycogen can be detected by PAS or PAS with diastase


  • Prominent uniform nucleoli


  • Most cases lack necrosis


  • Scattered wreath-like tumor giant cells


  • Occasional melanin pigment


  • Rare cases have nuclear pleomorphism


  • Most cases have few mitoses


ANCILLARY TESTS


Immunohistochemistry



  • Profile like that of melanoma in most cases



    • Occasional synaptophysin, CD56, epithelial membrane antigen, cytokeratin AE1/AE3, CD34


    • Negative α-smooth muscle actin, desmin, and cytokeratin CAM5.2


Cytogenetics



  • t(12;22)(q13;q12)



    • Most soft tissue cases


  • t(2;22)(q13;q12)



    • Often in gastrointestinal cases



PCR



  • Useful for diagnosis in unusual cases



    • EWS-ATF1 fusion (detectable by PCR)



      • Found in 90% of soft tissue cases


    • Alternate EWS-CREB1 fusion



      • Same transcripts found in angiomatoid fibrous histiocytoma (which has different morphology and prognosis)


      • Noted in gastrointestinal CCS that lack melanocytic differentiation


      • Cases express S100 protein but not melanocytic markers


    • Melanocyte-specific splice form of MITF transcript found in examples with melanocytic differentiation


Gene Expression Profiling



  • Has overlap with cutaneous melanoma profile

Jul 9, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Clear Cell Sarcoma
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