Abstract
Genetic changes associated with acute lymphoblastic leukemia (ALL) provide very important diagnostic and prognostic information with a direct impact on patient management. Detection of chromosome abnormalities by conventional cytogenetics combined with fluorescence in situ hybridization (FISH) play a very significant role in assessing risk stratification. Identification of specific chromosome abnormalities has led to the recognition of genetic subgroups based on reciprocal translocations, deletions and modal number in B or T-cell ALL. In the last twelve years 102 newly diagnosed childhood/adult ALL bone marrow samples were analysed for chromosomal abnormalities with conventional G-banding, and FISH (selected cases) using specific probes in our hospital. G-banded karyotype analysis found clonal numerical and/or structural chromosomal aberrations in 74.2% of cases. Patients with pseudodiploidy represented the most frequent group (38.7%) followed by high hyperdiploidy group (12.9%), low hyperdiploidy group (9.7%), hypodiploidy (<46) group (9.7%) and high hypertriploidy group (3.2%). The highest observed numerical chromosomal alteration was high hyperdiploidy (12.9%) with abnormal karyotypes while abnormal 12p (7.5%) was the highest observed structural abnormality followed by t(12;21)(p13.3;q22) resulting in ETV6/RUNX1 fusion (5.4%) and t(9;22)(q34.1;q11.2) resulting in BCR/ABL1 fusion (4.3%). Interestingly, we identified 16 cases with rare and complex structural aberrations. Application of the FISH technique produced major improvements in the sensitivity and accuracy of cytogenetic analysis with ALL patients. In conclusion it confirmed heterogeneity of ALL by identifying various recurrent chromosomal aberrations along with non-specific rearrangements and their association with specific immunophenotypes. This study pool is representative of paediatric/adult ALL patients in Oman.
Highlights
Acute lymphoblastic leukemia (ALL) is a heterogeneous form of haematological cancer consisting of various subtypes (Zakaria, 2012)
The detection of chromosome abnormalities by conventional cytogenetics combined with morphology, immunophenotype and especially with analyses using fluorescence in situ hybridization (FISH) is an important component in assessing the classification, sub classification, risk stratification and prediction of outcome of acute lymphoblastic leukemia (ALL) patients (Braekeleer et al, 2010)
40 (43%) patients were classified as precursor B ALL, 19 (21%) were B cell ALL, 24 (26%) T cell ALL, 2 (2%) were biphenotypic leukaemia, 3 (3%) were Null [non B, non T], and 5 (5%) were not done
Summary
Acute lymphoblastic leukemia (ALL) is a heterogeneous form of haematological cancer consisting of various subtypes (Zakaria, 2012). The detection of chromosome abnormalities by conventional cytogenetics combined with morphology, immunophenotype and especially with analyses using FISH is an important component in assessing the classification, sub classification, risk stratification and prediction of outcome of ALL patients (Braekeleer et al, 2010). In acute lymphoblastic leukaemia specific genomic abnormalities provide important clinical information. In most routine clinical diagnostic laboratories conventional karyotyping, in conjunction with targeted screens using e.g., FISH which is currently considered as the gold standard to detect such aberrations (Simons et al, 2011), plays a critical role in guiding targeted therapies, has evolved to become a vital diagnostic tool for personalized medicine (Linping, 2014) and reveal recurring chromosome abnormalities in approximately 80% of ALL cases, including numerical and structural changes, such as translocations, inversions, or deletions (Harrison et al, 2005; Moorman et al, 2010)
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