title: Unusual Clinical Presentation of Gastrointestinal Clear Cell Sarcoma.
abstract: BACKGROUND
  Use of molecular assays is gradually becoming a mandatory part of the clinical management of soft tissue tumors, however the choice and the interpretation of these tests may present a challenge.
  
  
  CONCLUSIONS
  This report demonstrates an unusual presentation of sarcoma, which was initially diagnosed as a tumor of unknown primary site. Given the presence of vimentin, Fli-1, CD99 and S100 markers, lack of immunostaining for melan A, HMB45, MITF, synaptophysin, CD56, myf4, CKAE1/3 and WT-1, as well as the presence of EWSR1 translocation determined by a break-apart FISH assay, Ewing's sarcoma (ES) diagnosis seemed to be well justified. However, polymerase chain reaction testing for ES-specific rearrangements (EWSR1/FLI1, EWSR1/ERG, EWSR1/ETV1, EWSR1/ETV4, EWS/FEV) failed to confirm the ES origin of the neoplastic tissue. We further considered clinical, morphological, immunohistochemical and molecular diagnostic features of other types of EWSR1-rearranged sarcomas and performed molecular testing for gastrointestinal clear cell sarcoma. The polymerase chain reaction assay revealed EWSR1ex7/ATF1ex5 fusion, thus confirming the latter diagnosis. Subsequent high-precision computed tomography of the abdominal cavity revealed a 5-cm tumor of the small bowel, which was subjected to surgical resection.
  
  
  CONCLUSIONS
  This report exemplifies that the use of anonymous cytogenetic assays, such as break-apart FISH EWSR1 testing, may not be sufficient even in case of a perfect match with relevant morphological and immunohistochemical tumor features.
  
  
  CONCLUSIONS
  Explicit identification of the translocation gene partners is indeed important for proper sarcoma diagnosis management.
authors.affiliation: Russian Research Center for Radiology and Surgical Technologies, Saint Petersburg, Russia.
authors.forename: Grigory A
authors.initials: GA
authors.lastname: Raskin
authors.affiliation: Russian Research Center for Radiology and Surgical Technologies, Saint Petersburg, Russia.
authors.forename: Kazimir M
authors.initials: KM
authors.lastname: Pozharisski
authors.affiliation: N.N. Petrov Institute of Oncology, Saint Petersburg, Russia ; Saint Petersburg State Pediatric Medical University, Saint Petersburg, Russia.
authors.forename: Aglaya G
authors.initials: AG
authors.lastname: Iyevleva
authors.affiliation: Saint Petersburg State University, Medical Faculty, Saint Petersburg, Russia.
authors.forename: Ivan V
authors.initials: IV
authors.lastname: Rikov
authors.affiliation: Saint Petersburg State University, Medical Faculty, Saint Petersburg, Russia.
authors.forename: Rashida V
authors.initials: RV
authors.lastname: Orlova
authors.affiliation: N.N. Petrov Institute of Oncology, Saint Petersburg, Russia ; Saint Petersburg State Pediatric Medical University, Saint Petersburg, Russia ; Saint Petersburg State University, Medical Faculty, Saint Petersburg, Russia ; I.I. Mechnikov North-Western State Medical University, Saint Petersburg, Russia.
authors.forename: Evgeny N
authors.initials: EN
authors.lastname: Imyanitov
keywords: ATF1; Cancer of unknown primary site; EWSR1; Ewing's sarcoma; Gastrointestinal clear cell sarcoma; Melanoma; Polymerase chain reaction; Review; Translocation