Cytogenetic place in managing myelodysplastic syndromes: an update by the Groupe francophone de cytogénétique hématologique (GFCH).

The myelodysplastic syndromes (MDS) are preleukemic diseases of elderly patients characterized by defective maturation of clonal hematopoietic progenitor cells resulting in peripheral blood cytopenias. Clonal chromosomal abnormalities are heterogeneous and can be detected in less than 50% of patients with de novo MDS and more frequently in secondary MDS (up to 80%). The karyotype plays an important role in the pathogenesis, diagnosis, and prognosis to evaluate the risk of leukemic transformation and, more recently, in treatment allocation. The gold standard for cytogenetic diagnosis in MDS is conventional chromosome banding analyses of bone marrow metaphases. The most frequent abnormalities are deletions and losses of chromosomes 5 (-5/5q-) and 7 (-7/7q-) and various isolated or combined abnormalities. Fluorescent in situ hybridization and array comparative genomic hybridization can reveal cryptic genetic abnormalities but are not recommended in routine diagnosis. New techniques including next generation sequencing revealed somatic driver mutations especially those affecting genes involved in RNA splicing or those harboring important prognostic value (TP53, ASXL1…) with potential applications in clinical practice in the future.