[Small cell type (Ewing-like) clear cell sarcoma of soft parts: a case report].

: The authors present a unique case of small cell variant of clear cell sarcoma of soft parts in a 42-year old woman. The tumor originally arose in the right flank of the soft tissues and ultimately developed both a local recurrence and multiple distant skin metastases two years and ten months thereafter. Nonspecific morphology of small blue round cell tumor was preserved at all microscopically verified sites and initially led to the spectrum of erroneous diagnoses such as an extraskeletal myxoid chondrosarcoma, Ewing sarcoma as well as malignant melanoma. The distinctive features of clear cell sarcoma such as fascicular nested growth pattern, spindling, clear cell change and/or eosinophilic cytoplasm were not disclosed even by extensive sampling. Immunohistochemically, the tumor expressed only S100protein and HMB45; all other markers (CD99, FLI1, cytokeratins, EMA) were completely negative. The molecular analysis carried out in one of the cutaneous metastases revealed translocation t(12;22) (EWSR1-ATF1) and ultimately led to the correct diagnosis of unusual Ewing-like clear cell sarcoma. Discussed is the implementation of molecular tests in routine diagnostics considering the existence of both histologically and biologically different tumors with an identical pathogenic molecular background.