Cytogenetics

Karyotyping or routine cytogenetic analysis helps detect clonal aberrations. It is an important diagnostic and prognostic tool because more than half of patients have an abnormal karyotype and the presence of t(8;21), inv(16), t(16;16), or t(15;17), which could impact response to treatment.1

Using conventional cytogenetic techniques, karyotype abnormalities are detected in only half of all acute myeloid leukemia (AML) cases.2

Fluorescence in situ hybridization (FISH) is a cytogenetic method that allows for the visual detection of a series of specific structural chromosome alterations, including translocations, inversions, amplifications or deletions of genes or genomic regions. It is most commonly used to confirm:

  • t(15;17) and its variants in acute promyelocytic leukemia (APL)
  • Detection of KMT2A (MLL) gene fusion partners

 
The speed of interphase FISH (iFISH) adds important diagnostic information, as it provides for an unequivocal diagnosis, or exclusion, of APL through the identification of the RARA-involved translocations.1

The third method of cytogenetics is using genomic hybridization techniques. These techniques allow for the detection of unbalanced genomic rearrangements (ie, gains or losses) in the whole genome. It is a valuable diagnostic approach because it identifies submicroscopic changes, especially in normal-karyotype (NK) AML and in analyses of poor banding quality.1

References: 1. Roug AS, Hansen MC, Nederby L, Hokland P. Diagnosing and following adult patients with acute myeloid leukaemia in the genomic age. Br J Haematol. 2014;167(2):162-176. 2. Bienz M, Ludwig M, Leibundgut EO, et al. Risk assessment in patients with acute myeloid leukemia and a normal karyotype. Clin Cancer Res. 2005;11(4):1416-1424.