title: Solitary fibrous tumor of the thigh with epithelioid features: a case report.
abstract: BACKGROUND
  Extrapleural Solitary Fibrous tumors (SFTs) have been increasingly reported. The retroperitoneum, deep soft tissues of proximal extremities, abdominal cavity, trunk, head and neck are the most common extraserosal locations reported. Microscopically they show a wide range of morphological features, and so the differential diagnosis is extensive. Immunohistochemically, they commonly express CD34, vimentin, bcl-2 and CD99. Epithelial membrane antigen (EMA) and smooth muscle actin (SMA) may occasionally be expressed. Epithelioid morphology in extrapleural SFT has only very occasionally been described (five cases reported), some of them with biphasic pattern and others with malignant characteristics.
  
  
  METHODS
  A SFT of the thigh with epithelioid areas in a 63 year old woman is reported. Microscopically the tumor showed areas hypo and hipercellular. At the periphery of the hipercellular areas there were nodules composed of epithelioid cells. Immunohistochemically both the spindle and epithelioid cells were positive for CD34, vimentin, bcl-2 and CD99. Epithelial, neural and muscular markers were negative. Molecular study was done and ruled out a synovial sarcoma.
  
  
  CONCLUSIONS
  Ten cases of SFT of the thigh have been reported but to our knowledge this is the first case with epithelioid morphology affecting the extremities. Identification of this pattern of SFT is of importance, to avoid misdiagnosis with other more aggressive conditions in soft tissue.
authors.affiliation: Department of Pathology, Hospital General Universitario, Valencia, Spain. miguel.martorell@uv.es
authors.forename: Miguel
authors.initials: M
authors.lastname: Martorell
authors.forename: Ana
authors.initials: A
authors.lastname: Pérez-Vallés
authors.forename: Francisco
authors.initials: F
authors.lastname: Gozalbo
authors.forename: Jose Angel
authors.initials: JA
authors.lastname: Garcia-Garcia
authors.forename: Jair
authors.initials: J
authors.lastname: Gutierrez
authors.forename: John
authors.initials: J
authors.lastname: Gaona