Bone marrow neoplastic

Bone marrow - neoplastic myeloid

Myelodysplastic syndromes / neoplasms (MDS)

MDS unclassifiable



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Last staff update: 20 July 2022

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PubMed Search: MDS unclassifiable

Nikhil Sangle, M.D.
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Cite this page: Sangle N. MDS unclassifiable. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/myeloproliferativeMDSNOS.html. Accessed May 29th, 2023.
Definition / general
Myelodysplastic syndrome, unclassifiable (MDS-U) diagnosis can be made in 3 instances:
  1. Unequivocal dysplasia < 10% in one or more lineage, with cytogenetic abnormalities presumptive of MDS, and < 1% blasts in peripheral blood, 5% blasts in bone marrow
  2. Refractory anemia or refractory cytopenia with multilineage dysplasia with 1% blasts in peripheral blood
  3. Unilineage dysplasia with pancytopenia

  • Cases can be reclassified into specific subtypes later if characteristic features develop
  • Some cases are associated with prior aplastic anemia and monosomy 7 (Am J Clin Pathol 2006;126:925)
  • Myelofibrosis: when present, often is difficult to obtain bone marrow aspirate; patients often have pancytopenia with dysplasia in 3 lineages; CD34 staining helps identify blast population
Case reports
Microscopic (histologic) images

AFIP images

Pancytopenia, abnormally bilobed nuclei in granulocytes

Marked increase in megakaryocytes

Erythroid hyperplasia

Large erythroid precursors


Hypercellular marrow with marked fibrosis

Cluster of large megakaryocytes

Marked reduction in megakaryocytes

Recurrence with increased marrow cellularity



Images hosted on other servers:

Megakaryocyte clustering and hyperlobulated forms (figs 2 / 3)

Differential diagnosis
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