Abstract:

The clear cell sarcomas of soft tissue are rare tumors originating from neural crest cells and presenting with poor prognosis. By the reason of the resemblance of histological properties to malign melanoma (eg. the im­munoreactivity to S100 and HMB45, the presence of me­lanosomes ultrastructurally), these tumors are also de­fined as malign melanomas of soft tissue. But distinctively from cutaneous melanoma, clear cell sarcoma is almost always deeply localized and the biological behaviour of the last one is also different. The differential diagnosis between clear cell sarcoma and desmoplastic or spindle cell malign melanoma may be more difficult because of the dermal localization of the last ones. In our case, it was observed an infiltrative tumor composed of uniform seeming cells with vesicular nuclei, distinct nucleoli, pale eosinophilic and sometimes clear, scant cytoplasms, in addition to necrotic areas. On immunohistochemical ex­amination, the tumoral cells showed a positive immunore­activity to vimentin, S100, HMB45, and SMA, while show­ing negative immunoreactivity with CD34, PanCK, EMA, LCA, CD99 and desmin. Ki-67 proliferation index was de­termined as approximately 50%. Because of deep local­ization and different morphological-immunohistochemical findings of the tumor, the case was diagnosed as “clear cell sarcoma”. It was observed a tumor with similar mor­phology in the biopsy sample taken from vertebra of the patient one month later than the first material and this was commented as the metastasis of the tumor to vertebra.

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