title: Primary subcutaneous spindle cell Ewing sarcoma with strong S100 expression and EWSR1-FLI1 fusion: a case report.
abstract: Ewing sarcoma is described classically as a small, round cell tumor of bone and soft tissue in children and young adults. Ewing sarcoma most often is characterized by a fusion of the Ewing sarcoma breakpoint region 1 (EWSR1) and the Friend leukemia virus integration 1 (FLI1) genes, forming an EWSR1-FLI1 fusion transcript. We report an exceptional case of primary subcutaneous Ewing sarcoma in a 16-year-old female composed entirely of spindle cells with focal fascicular growth and exhibiting strong, diffuse immunohistochemical reactivity for S100, unlike classic Ewing sarcoma. However, reverse transcription-polymerase chain reaction (RT-PCR) analysis confirmed the presence of a rare variant of the EWSR1-FLI1 fusion transcript, featuring fusion of EWSR1 exon 10 to FLI1 exon 6. To our knowledge, the combined histologic, molecular, and clinical features have not been reported previously in Ewing sarcoma, and raise a broad differential diagnosis emphasizing the importance of molecular techniques in the diagnosis of this tumor.
authors.affiliation: 1  Department of Pathology and Laboratory Medicine, The Ohio State University College of Medicine and Nationwide Children's Hospital, Columbus, OH, USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Arnold
authors.forename: Leomar Y
authors.initials: LY
authors.lastname: Ballester
authors.forename: Svetlana D
authors.initials: SD
authors.lastname: Pack
authors.forename: Ziedulla
authors.initials: Z
authors.lastname: Abdullaev
authors.forename: Melinda
authors.initials: M
authors.lastname: Merchant
authors.forename: Maria G
authors.initials: MG
authors.lastname: Tsokos
mesh_terms: D000293:Adolescent; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D014408:Biomarkers, Tumor / Q000032:analysis / Q000235:genetics; D059248:Chemoradiotherapy; D005260:Female; D050939:Gene Fusion; D020022:Genetic Predisposition to Disease; D006801:Humans; D007150:Immunohistochemistry; D015514:Oncogene Proteins, Fusion / Q000235:genetics*; D010641:Phenotype; D020133:Reverse Transcriptase Polymerase Chain Reaction; D009418:S100 Proteins / Q000032:analysis*; D012512:Sarcoma, Ewing / Q000737:chemistry* / Q000235:genetics* / Q000473:pathology / Q000628:therapy; D012878:Skin Neoplasms / Q000737:chemistry* / Q000235:genetics* / Q000473:pathology / Q000628:therapy; D016896:Treatment Outcome
chemical_list: D014408:Biomarkers, Tumor; C576197:EWSR1-FLI1 fusion protein, human; D015514:Oncogene Proteins, Fusion; D009418:S100 Proteins
keywords: EWSR1-FLI1; Ewing sarcoma; FISH; RT-PCR; S100; spindle cell