Soft tissue Ewing sarcoma-peripheral primitive neuroectodermal tumor with atypical clear cell pattern shows a new type of EWS-FEV fusion transcript

This study describes a new case of Ewing sarcoma (ES)peripheral primitive n euroectodermal tumor (pPNET) with unusual phenotype and fusion gene structu re. The tumor located in the inguinal area of a 15-year-old boy showed a hi ghly aggressive behavior with hematogenous metastases after intensive chemo therapy and bone marrow transplant, causing death 28 months after diagnosis . The tumor displayed a clear cell pattern, and several neuroectodermal mar kers proved positive both in the original tumor and in xenografts. This neu roectodermal character was confirmed by electron microscopy. Moreover, cyto genetically the tumor has an unusual chromosomal rearrangement, t(2;22)(q13 ;q22),t(3;18)(p21;q23), representing a new EWS-FEV fusion type in which exo n 7 of EWS gene is fused with exon 2 of FEV gene. This is the third publish ed study of an ES-pPNET showing EWS-FEV fusion described, but it is the fir st study of a tumor with the aforementioned fusion points. These findings s upport the genetic and morphologic heterogeneity existing within the group of ES-pPhTET tumors.