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Presented by Theresa Chan, M.D. and prepared by Anil Parwani, M.D.,Ph.D
Case 1: 27 year old female with a temporalis muscle mass.
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1. Question
Week 112: Case 1
27 year old female with a temporalis muscle mass./images/102802case1fig1.jpg
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/images/102802case1fig4.jpgCorrect
Answer: Clear cell sarcoma of soft tissue
Histology: The lesion consists of pale fusiform and cuboidal cells with large nuclei and prominent cherry red nucleoli arranged in large nests and fascicles. Mitoses are rare. The cytoplasm of the cells ranges from being clear to finely stippled and eosinophilic. Intracellular melanin can be seen in some of the cells. Deposits of hemosiderin can also be seen.
Discussion: Enzinger described clear cell sarcoma in 1968. The term malignant melanoma of soft parts is used as a synonym for these tumors. However, these tumors are distinct from malignant melanomas. Clear cell sarcomas tend to be deeply located and intimately associated with tendons or aponeuroses, and do not have epidermal involvement. They also show more uniform growth pattern. Differentiation between clear cell sarcoma and metastatic melanoma is difficult, as both lesions can show melanin pigment and express S100 proteins and HMB-45. Cytogenetic analysis may be required to reach a definitive diagnosis. Clear cell sarcomas have a distinct translocation, t(12;22)(q13;q12) resulting in a chimeric EWS/ATF1 fusion.
Clear cell sarcoma can be distinguished from synovial sarcoma by the absence of a biphasic pattern and intracelllular mucin, which are seen in synovial sarcoma, and the presence of intracellular melanin. The presence of melanin and a fusiform architecture, in addition to immunohistochemical stains for EMA, S100 and HMB45, can help to differentiate it from metastatic renal cell carcinoma.
Incorrect
Answer: Clear cell sarcoma of soft tissue
Histology: The lesion consists of pale fusiform and cuboidal cells with large nuclei and prominent cherry red nucleoli arranged in large nests and fascicles. Mitoses are rare. The cytoplasm of the cells ranges from being clear to finely stippled and eosinophilic. Intracellular melanin can be seen in some of the cells. Deposits of hemosiderin can also be seen.
Discussion: Enzinger described clear cell sarcoma in 1968. The term malignant melanoma of soft parts is used as a synonym for these tumors. However, these tumors are distinct from malignant melanomas. Clear cell sarcomas tend to be deeply located and intimately associated with tendons or aponeuroses, and do not have epidermal involvement. They also show more uniform growth pattern. Differentiation between clear cell sarcoma and metastatic melanoma is difficult, as both lesions can show melanin pigment and express S100 proteins and HMB-45. Cytogenetic analysis may be required to reach a definitive diagnosis. Clear cell sarcomas have a distinct translocation, t(12;22)(q13;q12) resulting in a chimeric EWS/ATF1 fusion.
Clear cell sarcoma can be distinguished from synovial sarcoma by the absence of a biphasic pattern and intracelllular mucin, which are seen in synovial sarcoma, and the presence of intracellular melanin. The presence of melanin and a fusiform architecture, in addition to immunohistochemical stains for EMA, S100 and HMB45, can help to differentiate it from metastatic renal cell carcinoma.
