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Surgical Pathology Criteria
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Myelodysplastic/Myeloproliferative Neoplasms with Isolated Isochromosome 17q

Definition

  • Unclassifiable myeldysplastic/myeloproliferative neoplasm (MDS/MPN-U) with isolated isochromosome 17q

Note

  • This is a newly recognized entity not specifically categorized in the WHO 2008 edition

Diagnostic Criteria

  • Meets criteria for MDS/MPN-U
    • Must have both myelodysplastic and myeloproliferative features
    • Must not satisfy criteria for any defined myeloid neoplasm
  • Demonstrates isochromosome 17q as the sole or primary cytogenetic abnormality
    • Molecular pathology evidence of other mutations occasionally seen
  • Characteristic features
    • Pseudo-Pelger-Huet-like neutrophils
    • Micromegakaryocytic hyperplasia
    • Marrow hypercellularity, fibrosis, and osteosclerosis
    • Increased marrow blasts (definitionally <20% in this category)
  • Short overall survival
    • High risk of leukemic transformation

Differential Diagnosis

  • This is a diagnosis of exclusion
    • Isochromosome 17 may be seen as a primary or secondary cytogenetic abnormality in other myeloid neoplasms, which must first be excluded

Dita Gratzinger MD PhD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting: 11/6/11

Myelodysplasia is defined by morphologic features of abnormal cellular maturation in at least one bone marrow lineage

  • Not all features are applicable to all disorders
  • Dyserythropoeisis
    • Peripheral blood erythrocyte abnormalities
      • Normocytic, normochromic anemia
      • Macrocytosis
      • Dimorphic red blood cells (RBC)
      • Basophilic stippling
      • Poikilocytosis
        • Varying shapes, frequently macro-ovalocytes
    • Bone marrow erythroid lineage abnormalties
      • Erythroid hyperplasia or hypoplasia
        • Megaloblastoid / megaloblastic changes
          • Dyssynchronous maturation of nucleus and cytoplasm of erythroid precursors
            • Nucleus lags behind cytoplasm
      • Ring sideroblasts
        • ≥5 iron granules encircling ≥1/3 of the nucleus
        • Usually either many or none
      • Cytoplasmic vacuoles
        • Also seen in copper deficiency
      • Nuclear changes
        • Multinuclearity
        • Nuclear budding, hyperlobulation and satellite nuclei
        • Internuclear bridging
  • Dysgranulopoiesis
    • Peripheral blood and/or bone marrow findings (easier seen in peripheral blood)
      • Hypogranularity
        • Pale cytoplasm almost indistinguishable from background on slide
      • Nuclear hypolobation or irregular hypersegmentation (>5 lobes)
        • Pseudo Pelger-Huet anomaly
          • Two equal size nuclear lobes connected by a thin strand of chromatin
      • Infrequent findings
        • Abnormal cytoplasmic granules (pseudo Chediak-Higashi granules)
          • Giant grey to red granules
        • Dohle bodies
          • Small blue cytoplasmic inclusions
          • Often found at periphery of cell
        • Auer rods
          • Rod-like structures formed by fusion of primary granules
          • May be found in blasts or maturing granulocytes
  • Dysmegakaryopoiesis
    • Peripheral blood platelet abnormalities
      • Giant
        • Larger than a red blood cell
      • Bizarre
        • Irregular shapes and protrusions
      • Hypogranularity
        • Compare to normal platelets with purple granules
    • Bone marrow megakaryocyte abnormalities
      • Micromegakaryocytes
        • Smaller than a promyelocyte
      • Nuclear hypolobation
        • Prominent in 5q- syndrome
        • A single lobe is typically seen in a small megakaryocyte
      • Multinucleation
        • Distinct nuclei without a connecting strand of chromatin
      • Cytoplasmic hypogranularity

Classification / Lists

WHO 2008 Classification of Myeloid Neoplasms

Myeloproliferative Neoplasms (MPN)

Myeloid and lymphoid neoplasms with eosinophilia and abnormalities of PDGFRA, PDGFRB or FGFR1

Myelodysplastic/Myeloproliferative Neoplasms (MDS/MPN)

Myelodysplastic Syndromes (MDS)

Therapy Related Myeloid Neoplasms

 

Bibliography

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