title: Primary Synovial Sarcoma (SS) of the digestive system: a molecular and clinicopathological study of fifteen cases.
abstract: BACKGROUND
  Recently a few cases of synovial sarcoma (SS) of the abdominal viscera have been reported, raising awareness about the potential for confusion between this entity and KIT-negative gastrointestinal stromal tumors (GIST). We report the clinicopathological, immunophenotypical and molecular features of fifteen more SS occurring in the stomach (8 cases), epigastric region (one case), small intestine (one case), large intestine (three cases), involving both the terminal ileum and the caecum (one case) and liver (one case).
  
  
  METHODS
  Immunostains for SMA, DESMIN, CD34, CD117, S100, EMA, CK AE1/3, TLE1, CD56, CD99, BCL2, DOG1 were performed. Rearrangement of SS18 gene region was screened in all cases: by conventional karyotype in one case, the remaining cases were screened either by interphase FISH or Q-PCR or both.
  
  
  RESULTS
  Ten patients were male and five female, with an age range of 17-61 years (median 44). Tumor size ranged from 2 to 15 cm (median 8). Mitoses per 10 HPF ranged from 4 to 27 (median 9.5). Eleven tumors were monophasic fibrous SS, one biphasic SS and three poorly differentiated SS. SMA, Desmin, CD34, CD117 and S100 were negative in all cases, whereas EMA and/or CK AE1/AE3 were positive in all cases. TLE1, BCL2 and CD56 were positive in all tested cases. DOG1 was positive in one case. SS18 gene region rearrangement was demonstrated in all cases. A fusion transcript was amplified in eight cases: either SS18-SSX2 or SS18-SSX1 respectively in four cases each.
  
  
  CONCLUSIONS
  SS is increasingly recognized at visceral sites. Molecular analyses play a key role when dealing with usual histotypes in unusual sites. Correct diagnosis is crucial for appropriate therapy.
authors.affiliation: Department of Pathology, Treviso Regional Hospital, Piazza Ospedale 1, 31100 Treviso, Italy.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Romeo
authors.affiliation: Department of Pathology, Treviso Regional Hospital, Piazza Ospedale 1, 31100 Treviso, Italy.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Rossi
authors.affiliation: Departments of Pathology, The University of Texas M. D. Anderson Cancer Center, Houston, TX USA.
authors.forename: Marthelena
authors.initials: M
authors.lastname: Acosta Marín
authors.affiliation: Department of Pathology, Treviso Regional Hospital, Piazza Ospedale 1, 31100 Treviso, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Canal
authors.affiliation: Department of Pathology, Treviso Regional Hospital, Piazza Ospedale 1, 31100 Treviso, Italy.
authors.forename: Marta
authors.initials: M
authors.lastname: Sbaraglia
authors.affiliation: Department of Pathology, Treviso Regional Hospital, Piazza Ospedale 1, 31100 Treviso, Italy.
authors.forename: Licia
authors.initials: L
authors.lastname: Laurino
authors.affiliation: Department of Pathology, Bolzano Regional Hospital, Bolzano, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Mazzoleni
authors.affiliation: Department of Pathology, Padua University Medical School, Padua, Italy.
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Montesco
authors.affiliation: Department of Pathology, Treviso Regional Hospital, Piazza Ospedale 1, 31100 Treviso, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Valori
authors.affiliation: Department of Pathology, Treviso Regional Hospital, Piazza Ospedale 1, 31100 Treviso, Italy.
authors.forename: Marta
authors.initials: M
authors.lastname: Campo Dell'Orto
authors.affiliation: Department of Pathology, Ospedali Riuniti di Bergamo, Bergamo, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Gianatti
authors.affiliation: Departments of Pathology, The University of Texas M. D. Anderson Cancer Center, Houston, TX USA.
authors.forename: Alexander Joseph
authors.initials: AJ
authors.lastname: Lazar
authors.affiliation: Department of Pathology, Treviso Regional Hospital, Piazza Ospedale 1, 31100 Treviso, Italy.
authors.forename: Angelo Paolo
authors.initials: AP
authors.lastname: Dei Tos
keywords: Differential diagnosis; Digestive tract; Pathology; Sarcoma; Synovial sarcomas