What is the World Health Organization (WHO) algorithm for determining unclassifiable myelodysplastic syndromes (MDS-U)?

Updated: Jul 21, 2020
  • Author: Robert P Hasserjian, MD; Chief Editor: Christine G Roth, MD  more...
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The 2016 revised World Health Organization (WHO) classification recognizes three distinct scenarios that form the unclassifiable myelodysplastic syndromes (MDS-U) group, as follows [3, 4] :

  • Cases of myelodysplastic syndrome (MDS) with less than 5% bone marrow blasts that have 1% blasts in the peripheral blood, documented on at least two separate occasions

  • Cases of MDS with dysplasia limited to one lineage (MDS with single lineage dysplasia [MDS-SLD], MDS with ring sideroblasts and single lineage dysplasia [MDS-RS-SLD]) that have pancytopenia (hemoglobin < 10 g/dL, absolute neutrophil count [ANC] < 1.8 x 109/L [see the Absolute Neutrophil Count calculator], and platelet count < 100 x 109/L)

  • Cases presenting with persistent, unexplained cytopenia(s) that lack the diagnostic morphologic features of MDS but bear a specific clonal bone marrow cytogenetic abnormality (see the section on Immunophenotypic and Cytogenetic Features).

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