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Chronic Myeloid Neoplasms

Myelodysplastic syndromes

MDS, unclassified


Reviewer: Nikhil Sangle, M.D. (see Reviewers page)
Revised: 12 August 2011, last major update August 2011
Copyright: (c) 2001-2011, PathologyOutlines.com, Inc.

Definition
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Myelodysplastic syndrome, unclassifiable (MDS-U) diagnosis can be made in 3 instances:
(a) 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
(b) Refractory anemia or refractory cytopenia with multilineage dysplasia with 1% blasts in peripheral blood
(c) 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
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● 82 year old man with moderate thrombocytopenia (University of Pittsburgh Case #520)

Micro images
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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


Megakaryocyte clustering and hyperlobulated forms (figs 2/3)

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

Differential diagnosis
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● Acute panmyelosis with myelofibrosis (20% or more blasts), AML-M7 (20% or more blasts), chronic idiopathic myelofibrosis (usually marked splenomegaly, no dysplasia)

End of Chronic Myeloid Neoplasms > Myelodysplastic syndromes > MDS, unclassified


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