Chronic Myeloid Neoplasms
Myelodysplastic syndromes
MDS, unclassified

Author: Nikhil Sangle, M.D. (see Authors page)

Revised: 28 February 2017, last major update August 2011

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PubMed Search: MDS unclassified

Cite this page: MDS, unclassified. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/myeloproliferativeMDSNOS.html. Accessed March 28th, 2017.
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
Micro Images

Images hosted on PathOut server:


Bone marrow smear:

59 year old woman with pancytopenia,
abnormally bilobed nuclei in granulocytes,
red cell (upper left) has lobulated nucleus, no increase in blasts,
monocytes or ringed sideroblasts, could not classify


37 year old man with monosomy 5 and 7, pancytopenia:

Marked increase in
megakaryocytes,
many with
hyperlobulated nuclei

Erythroid hyperplasia with
marked dyserythropoiesis
and megaloblastoid
changes

Large erythroid precursors with
hyperlobulated nuclei, also ringed
sideroblasts (< 15%), occasional dysplastic
neutrophils, no increase in myeloblasts


6 year old girl with trisomy 8, severe anemia and 1 - 2% blasts in peripheral blood:

Hypercellular marrow with
marked fibrosis, increased
megakaryocytes (singly and in clusters)
and scattered erythroid islands

Cluster of large
megakaryocytes with
abnormal nuclear lobulation
and adjacent erythroid precursors

Bone marrow biopsy post allogeneic
bone marrow transplant shows marked
reduction in megakaryocytes, overall
cellularity and connective tissue

Bone marrow biopsy one month
post transplant shows recurrence
with increased marrow cellularity
and prominent megakaryocytes


Images hosted on other servers:


Bone marrow smear:

Megakaryocyte clustering and hyperlobulated forms (figs 2 / 3)

Differential Diagnosis