Ewing's sarcoma and peripheral primitive neuroectodermal tumor in adults: different features of a rare neoplasm.

INTRODUCTION: In adults, peripheral primitive neuroectodermal tumors (pPNETs) represent a rare and heterogeneous group of neoplasms exhibiting neuronal and glial differentiation.

PATIENTS AND METHODS: We present the clinicopathologic features of four examples of the Ewing's sarcoma (EWS)/pPNET group in adults. Hematoxylin and eosin staining, immunohistochemical and molecular studies were reviewed in every case. Immunohistochemical stains were performed on formalin-fixed, paraffin-embedded sections, molecular studies were done using fluorescence in situ hybridization (FISH).

RESULTS: Three patients presented with tumors of the thoracopulmonary region, one patient showed EWS of the soft tissue. Microscopically, tumor tissue was composed of round, small, blue cells with fine granular chromatin texture and inconspicuous nucleoli. Mitotic figures and rosettes were present. Tumor cells strongly coexpressed CD99 and vimentin, but due to technical reasons t(22q12) translocation studies proved the presumptive diagnosis of EWS/pPNET in one case only. Despite similar multimodality treatment survival time ranged from 6 to 42 months, two patients were alive at the time of reporting.

CONCLUSIONS: As tumors of the EWS/pPNET family behave aggressively, rapid diagnosis is warranted. Since diagnosis of EWS/pPNET requires ancillary studies, it is necessary to consider it even in adult patients.