title: Diversity of breakpoints of variant Philadelphia chromosomes in chronic myeloid leukemia in Brazilian patients.
abstract: BACKGROUND
  Chronic myeloid leukemia is a myeloproliferative disorder characterized by the Philadelphia chromosome or t(9;22)(q34.1;q11.2), resulting in the break-point cluster region-Abelson tyrosine kinase fusion gene, which encodes a constitutively active tyrosine kinase protein. The Philadelphia chromosome is detected by karyotyping in around 90% of chronic myeloid leukemia patients, but 5-10% may have variant types. Variant Philadelphia chromosomes are characterized by the involvement of another chromosome in addition to chromosome 9 or 22. It can be a simple type of variant when one other chromosome is involved, or complex, in which two or more chromosomes take part in the translocation. Few studies have reported the incidence of variant Philadelphia chromosomes or the breakpoints involved among Brazilian chronic myeloid leukemia patients.
  
  
  OBJECTIVE
  The aim of this report is to describe the diversity of the variant Philadelphia chromosomes found and highlight some interesting breakpoint candidates for further studies.
  
  
  METHODS
  the Cytogenetics Section Database was searched for all cases with diagnoses of chronic myeloid leukemia during a 12-year period and all the variant Philadelphia chromosomes were listed.
  
  
  RESULTS
  Fifty (5.17%) cases out of 1071 Philadelphia-positive chronic myeloid leukemia were variants. The most frequently involved chromosome was 17, followed by chromosomes: 1, 20, 6, 11, 2, 10, 12 and 15.
  
  
  CONCLUSIONS
  Among all the breakpoints seen in this survey, six had previously been described: 11p15, 14q32, 15q11.2, 16p13.1, 17p13 and 17q21. The fact that some regions get more frequently involved in such rare rearrangements calls attention to possible predisposition that should be further studied. Nevertheless, the pathological implication of these variants remains unclear.
authors: Universidade Federal de São Paulo (UNIFESP), São Paulo, SP, Brazil; Grupo Fleury, São Paulo, SP, Brazil.
authors: Maria de Lourdes Lopes Ferrari
authors: Mde L
authors: Chauffaille
authors: Grupo Fleury, São Paulo, SP, Brazil. Electronic address: anacarolusp@gmail.com.
authors: Ana Carolina de Almeida
authors: AC
authors: Bandeira
authors: Grupo Fleury, São Paulo, SP, Brazil.
authors: Aline Schiavoni Guarnieri
authors: AS
authors: da Silva
keywords: Brazil; Chromosome breakpoints; Leukemia, myelogenous, chronic, BCR-ABL positive; Oncogenes; Philadelphia chromosome
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