title: Fine needle aspiration appearance of extragastrointestinal stromal tumor. A case report.
abstract: BACKGROUND
  Gastrointestinal stromal tumors (GISTs) rarely develop outside the digestive tract and in the soft tissues of abdomen and retroperitoneum. Such tumors are designated extra-GISTs (EGISTs). Cytologic and immunocytochemical features of a case of EGIST are reported.
  
  
  METHODS
  A 54-year-old woman presented with a peritoneal mass, diameter 22 cm, adherent to the omentum and without a connection to the digestive tract. Fine needle aspiration biopsy (FNAB) of the excised tumor showed high cellularity in two patterns: monotonous spindle cells were intermingled with a mildly atypical epithelioid component. Immunocytochemistry performed on cytospins revealed reactivity for c-kit (CD117), CD34 and smooth muscle actin and negativity for S-100. The findings were concordant with a histologic diagnosis of EGIST.
  
  
  CONCLUSIONS
  EGISTs are infrequent neoplasms and can be diagnosed in FNAB samples. The clinical/radiologic setting must be considered together with the cytologic features. Immunocytochemistry is a clue to the diagnosis when it detects c-kit reactivity.
authors.affiliation: Department of Pathology, Policlínico de Vigo, S.A., Vigo, Pontevedra, Spain. jaortiz@povisa.es
authors.forename: José A
authors.initials: JA
authors.lastname: Ortiz-Rey
authors.forename: Gabriel C
authors.initials: GC
authors.lastname: Fernández
authors.forename: Carlos J
authors.initials: CJ
authors.lastname: Magdalena
authors.forename: Carlos
authors.initials: C
authors.lastname: Alvarez
authors.forename: Iosu
authors.initials: I
authors.lastname: Antón
authors.forename: Pilar
authors.initials: P
authors.lastname: San Miguel
authors.forename: Ana
authors.initials: A
authors.lastname: de la Fuente
mesh_terms: D000008:Abdominal Neoplasms / Q000737:chemistry / Q000473:pathology* / Q000601:surgery; D000199:Actins / Q000032:analysis; D018952:Antigens, CD34 / Q000032:analysis; D014408:Biomarkers, Tumor / Q000032:analysis; D001707:Biopsy, Needle / Q000379:methods*; D005260:Female; D005770:Gastrointestinal Neoplasms / Q000737:chemistry / Q000473:pathology* / Q000601:surgery; D006801:Humans; D007150:Immunohistochemistry; D008875:Middle Aged; D009852:Omentum / Q000737:chemistry / Q000473:pathology / Q000601:surgery; D010534:Peritoneal Neoplasms / Q000737:chemistry / Q000473:pathology* / Q000601:surgery; D019009:Proto-Oncogene Proteins c-kit / Q000032:analysis; D017154:Stromal Cells / Q000737:chemistry / Q000473:pathology; D014057:Tomography, X-Ray Computed
chemical_list: D000199:Actins; D018952:Antigens, CD34; D014408:Biomarkers, Tumor; D019009:Proto-Oncogene Proteins c-kit