title: Derivative chromosome 9 deletions in chronic myeloid leukaemia: interpretation of atypical D-FISH pattern.
abstract: OBJECTIVE
  New molecular cytogenetic techniques are increasingly applied as a routine investigative tool in haematological malignancies, both at diagnosis and subsequent monitoring. This report describes the interpretation of atypical signal patterns encountered using BCR-ABL dual colour dual fusion fluorescence in situ hybridisation (D-FISH) translocation probes in chronic myeloid leukaemia (CML).
  
  
  METHODS
  Interphase FISH experiments were carried out using BCR-ABL D-FISH probes in 46 patients with CML at diagnosis and during subsequent disease monitoring. Atypical hybridisation signal patterns were characterised by molecular cytogenetic techniques and correlated with conventional karyotyping.
  
  
  RESULTS
  Two patients showed atypical interphase D-FISH patterns with one orange, one green, and one fusion (1O1G1F) signal. The presence of BCR-ABL gene fusion was documented by a dual colour single fusion (S-FISH) probe. The submicroscopic deletion of the ABL-BCR fusion gene on the derivative chromosome 9 in these cases was subsequently characterised by metaphase FISH on relocated G banded metaphases.
  
  
  CONCLUSIONS
  Atypical interphase D-FISH patterns should not be interpreted in isolation and should be considered in conjunction with other cytogenetic or molecular genetic investigations.
authors.affiliation: Department of Pathology, The University of Hong Kong, Queen Mary Hospital, Pokfulam Road, Hong Kong, PR China.
authors.forename: T S K
authors.initials: TS
authors.lastname: Wan
authors.forename: S K
authors.initials: SK
authors.lastname: Ma
authors.forename: W Y
authors.initials: WY
authors.lastname: Au
authors.forename: L C
authors.initials: LC
authors.lastname: Chan
mesh_terms: D000328:Adult; D000368:Aged; D002872:Chromosome Deletion; D002899:Chromosomes, Human, Pair 9 / Q000235:genetics*; D005260:Female; D016044:Fusion Proteins, bcr-abl / Q000235:genetics; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000235:genetics*; D008297:Male
chemical_list: D016044:Fusion Proteins, bcr-abl