title: Fluorescence in situ hybridization patterns of BCR/ABL1 fusion in chronic myelogenous leukemia at diagnosis.
abstract: BACKGROUND
  Chronic myelogenous leukemia (CML) is characterised by the t(9;22)(q34;q11.2) which results in the formation of the BCR/ABL1 fusion gene. Occasionally, the t(9;22) may be associated with submicroscopic deletions of chromosomes 9 and/or 22 which appear to be associated with a worse prognosis. Three or four-way variant t(9;22) may also occur. All these changes as well as gain of the Philadelphia chromosome which represents disease progression can be detected by fluorescence in situ hybridization (FISH) analysis. FISH analysis at presentation is used to determine the number of cells with BCR/ABL1 fusion and establish whether the patterns are typical or atypical. Response to therapy can then be monitored by serial testing.
  
  
  METHODS
  The study group consisted of all patients diagnosed or suspected to have CML who had interphase FISH analysis at presentation on peripheral blood/bone marrow using a commercially available BCR/ABL1 dual colour, dual fusion probe. The study was performed at a tertiary hospital in India between 2004 and 2010.
  
  
  RESULTS
  There were 1076 diagnostic samples which were positive for BCR/ABL1 fusion. Typical dual fusion signals (two fusions, one red and one green, 2F1R1G) were seen in 801 cases (74 %). Atypical signal patterns were seen in 275 cases (26%). These were: 1F1R2G (4%), 1F2R1G (2.5%) and 1F1R1G (11%) representing deletions of the derivative 9 involving chromosome 9 sequences, chromosome 22 sequences, or both respectively; 3F1R1G (6.5%) usually representing gain of an additional Philadelphia chromosome and 1F2R2G (1%) representing a three- or four-way variant translocation. More than one signal pattern was seen in 1%.
  
  
  CONCLUSIONS
  Our findings were similar to the literature with respect to the distribution of signal patterns except that we had a lower number of patients with variant translocations. While each signal pattern is typically associated with a particular abnormality, there can be more than one explanation for each pattern. Hence, metaphase FISH analysis is the "gold standard" for the interpretation of signal patterns.
authors.affiliation: Cytogenetics Unit, Christian Medical College, Vellore, Tamilnadu, India.
authors.forename: Poonam P
authors.initials: PP
authors.lastname: Jain
authors.forename: Mayur
authors.initials: M
authors.lastname: Parihar
authors.forename: Rayaz
authors.initials: R
authors.lastname: Ahmed
authors.forename: Aby
authors.initials: A
authors.lastname: Abraham
authors.forename: Auro
authors.initials: A
authors.lastname: Vishwabandya
authors.forename: Biju
authors.initials: B
authors.lastname: George
authors.forename: Vikram
authors.initials: V
authors.lastname: Mathews
authors.forename: Alok
authors.initials: A
authors.lastname: Srivastava
authors.forename: Vivi M
authors.initials: VM
authors.lastname: Srivastava
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D005260:Female; D016044:Fusion Proteins, bcr-abl / Q000235:genetics*; D006801:Humans; D017404:In Situ Hybridization, Fluorescence / Q000379:methods*; D007194:India; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D015345:Oligonucleotide Probes / Q000737:chemistry / Q000235:genetics; D062606:Tertiary Care Centers; D055815:Young Adult
chemical_list: D015345:Oligonucleotide Probes; C406060:abl-bcr fusion protein, human; D016044:Fusion Proteins, bcr-abl