title: Primary Extra-gastrointestinal Stromal Tumor of Retroperitoneum.
abstract: BACKGROUND
  Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract. More rarely neoplasms with histology and immunohistochemistry similar to GISTs may occur outside the gastrointestinal tract ( omentum, mesentery and retroperitoneum) and are so-called Extra-gastrointestinal Stromal Tumors (EGISTs). EGISTs arising in the retroperitoneum are extremely rare: to date, only 58 cases have been reported in the literature.
  
  
  METHODS
  We herein report a case of a primary EGIST of the retroperitoneum surgically treated. The pre-operative radiological evaluation showed a retroperitoneal mass, placed in left paravertebral region.
  
  
  RESULTS
  Morphological and immunohistochemical features led to a diagnosis of extra-gastrointestinal stromal tumor (intermediate-low risk form).
  
  
  CONCLUSIONS
  As a result of the rarity of reports of primary EGISTs of retroperitoneum we need to analyze the data of reported cases in order to gain a better understanding about the pathogenesis, prognosis and optimal treatment of this disease.
authors.affiliation: Department of Medical and Surgical Sciences, University of Brescia, 1st Division of General Surgery-Spedali Civili Brescia, Brescia, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Casella
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Villanacci
authors.forename: Filippo
authors.initials: F
authors.lastname: D'Adda
authors.forename: Manuela
authors.initials: M
authors.lastname: Codazzi
authors.forename: Bruno
authors.initials: B
authors.lastname: Salerni