title: Primary CD56 positive lymphomas of the gastrointestinal tract.
abstract: BACKGROUND
  Primary CD56 positive lymphoma of the gastrointestinal (GI) tract is rare. Genotypically, these tumors can be classified into natural killer (NK)-like T-cell lymphoma or NK cell lymphoma by the presence or absence of T-cell receptor (TCR) gene rearrangement. However, they have a considerable degree of morphologic and immunophenotypic overlap, making a definitive diagnosis difficult.
  
  
  METHODS
  The clinicopathologic features of three patients with primary CD56 positive lymphoma of the small and large bowel are presented. This is followed by a review of the English literature from 1966 to the present.
  
  
  RESULTS
  All patients had CD56 positive/CD3epsilon positive disease on paraffin section. Two patients were positive for Epstein-Barr virus-encoded early nuclear RNAs (EBER) according to in situ histochemistry results and were negative for TCR gene rearrangement, consistent with primary NK lymphoma of the GI tract. The other patient was EBER negative with rearranged TCR, consistent with NK-like T-cell lymphoma. There was no clinical or histologic evidence of enteropathy in any of the patients. The major presenting symptoms included fever, weight loss, and intestinal perforation. All patients died between 1 week and 6 months after diagnosis despite undergoing surgery and intensive chemotherapy.
  
  
  CONCLUSIONS
  These results, together with a literature review, suggest that primary NK cell lymphoma of the GI tract may be considered a distinct clinicopathologic entity. Both primary NK and NK-like T-cell lymphoma pursue an aggressive clinical course. EBER and TCR gene rearrangement are useful in distinguishing NK cell lymphoma from NK-like T-cell lymphoma, particularly when frozen tissue is not available for immunophenotyping.
authors.affiliation: Department of Medicine, Queen Mary Hospital, University of Hong Kong, Hong Kong, China. jcschim@hkucc.hku.hk
authors.forename: C S
authors.initials: CS
authors.lastname: Chim
authors.forename: W Y
authors.initials: WY
authors.lastname: Au
authors.forename: T W
authors.initials: TW
authors.lastname: Shek
authors.forename: J
authors.initials: J
authors.lastname: Ho
authors.forename: C
authors.initials: C
authors.lastname: Choy
authors.forename: S K
authors.initials: SK
authors.lastname: Ma
authors.forename: H M
authors.initials: HM
authors.lastname: Tung
authors.forename: R
authors.initials: R
authors.lastname: Liang
authors.forename: Y L
authors.initials: YL
authors.lastname: Kwong
mesh_terms: D000328:Adult; D000368:Aged; D019002:CD56 Antigen / Q000032:analysis*; D005260:Female; D006801:Humans; D007414:Intestinal Neoplasms / Q000276:immunology* / Q000473:pathology; D016399:Lymphoma, T-Cell / Q000276:immunology* / Q000473:pathology; D008297:Male; D008875:Middle Aged
chemical_list: D019002:CD56 Antigen