title: CD56 expression in acute promyelocytic leukemia: a possible indicator of poor treatment outcome?
abstract: OBJECTIVE
  Blast expression of CD56 is frequent in patients with t(8;21)(q22;q22) acute myeloid leukemia and is associated with an inferior outcome. The expression of CD56 has rarely been reported in acute promyelocytic leukemia (APL) and has not been clinically characterized. Therefore, we examined the prognostic significance of CD56 expression in APL.
  
  
  METHODS
  We identified all reported cases of CD56+ APL in the medical literature and collected clinical, biologic, and therapeutic details.
  
  
  RESULTS
  Data were obtained for 12 patients with CD56+ APL (> 20% blast expression of CD56), including four cases from a single institution with a total of 42 APL patients. All of the CD56+ APL patients had documented cytogenetic presence of t(15;17), and of the nine reported isotypes, eight (89%) were S-isoform. Only six CD56+ patients (50%) attained complete remission (CR); the other six individuals died within 35 days of presentation. Of the six patients who attained a CR, three (50%) relapsed at 111, 121, and 155 weeks, whereas three remained in continuous CR at 19, 90, and 109 weeks. Comparison of the control CD56- to CD56+ APL patients demonstrated that the latter group had a significantly lower fibrinogen level (P = .007), and among patients for whom data were available, there was a higher frequency of the S-isoform (P = .006). Additionally, the CR rate (50% v 84%, P = .025) and overall median survival (5 v 232 weeks; P = .019) were significantly inferior for CD56+ APL patients.
  
  
  CONCLUSIONS
  CD56+ acute promyelocytic leukemia is infrequent, seems to occur more frequently with the S-isoform subtype, and may be associated with a lower CR rate and inferior overall survival.
authors.affiliation: Walter Reed Army Medical Center, Washington, DC 20307, USA.
authors.forename: C K
authors.initials: CK
authors.lastname: Murray
authors.forename: E
authors.initials: E
authors.lastname: Estey
authors.forename: E
authors.initials: E
authors.lastname: Paietta
authors.forename: R S
authors.initials: RS
authors.lastname: Howard
authors.forename: W J
authors.initials: WJ
authors.lastname: Edenfield
authors.forename: S
authors.initials: S
authors.lastname: Pierce
authors.forename: K P
authors.initials: KP
authors.lastname: Mann
authors.forename: C
authors.initials: C
authors.lastname: Bolan
authors.forename: J C
authors.initials: JC
authors.lastname: Byrd
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019002:CD56 Antigen / Q000032:analysis*; D005260:Female; D006801:Humans; D016130:Immunophenotyping; D015473:Leukemia, Promyelocytic, Acute / Q000276:immunology / Q000401:mortality / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D012008:Recurrence; D012074:Remission Induction; D012189:Retrospective Studies; D012307:Risk Factors; D015996:Survival Rate; D016896:Treatment Outcome
chemical_list: D019002:CD56 Antigen