Surgical Pathology Criteria–

Essential Thrombocythemia

Differential Diagnosis

Secondary Thrombocythemia

Hematolymphoid Disorders with Thrombocytosis
  CML PV PMF, Cellular Phase ET RARS-T 5q-
Tyrosine kinase ABL p230 variant* JAK2 JAK2 or MPL 50% JAK2 or MPL 50% JAK2 50% JAK2 or MPL 10%
Blood ↑PMN, basophils, platelets Normo or hypochromatic anemia, may have ↑basophils, platelets Anemia, leukocytosis, ↑or nl platelets ↑platelets, often abnormal Dimorphic RBC, ↑platelets Macrocytic anemia, ↑or nl platelets
Marrow ↑↑Myeloids, ↑dwarf megas Panmyelosis, ±erythroid hyperplasia, atypical megas Panmyelosis, atypical tightly clustered megas ↑↑Megas Erythroid dysplasia, ring sideroblasts, ↑megas Erythroid hypoplasia, ↑small megas
Marrow Fibrosis Varies ↑ in spent phase ↑↑ in fibrotic phase Minimal Varies Minimal
Splenomegaly ++ ++ +++ ± ± Absent
Clinical/Other B symptoms Hypertension, thrombosis, pruritus, ↓EPO B symptoms, bleeding, gout Thrombosis, hemorrhage Anemia Anemia
EPO = erythropoietin, * rare p230 BCR-ABL1 isoform can present with thrombocytosis and /or neutrophilia

 

Essential Thrombocythemia vs Cellular Phase Primary Myelofibrosis vs CML
  Essential Thrombocythemia Cellular Phase Primary Myelofibrosis CML with p230
Cellularity Normal to moderately hypercellular Markedly hypercellular (cellular phase) Markedly hypercellular
Megas - Distribution Dispersed or loose clusters Tight clusters, touching each other Dispersed or loose clusters
Megas - Size Large and giant Pleomorphic Variable, may have dwarf forms
Megas - Nuclei Lobulated Bulbous, hyperchromatic Hypolobated
Megas - Cytoplasm Mature Variable, may have naked nuclei Mature
Granulopoietic Hyperplasia Infrequent, mild Moderate to marked in cellular phase Marked
Splenomegaly Infrequent Frequent Rare
JAK2V617I Allele burden <50% Allele burden >50%  
Megas = megakaryocytes

Common Myeloproliferative Neoplasms - Overview
  CML PV PMF ET
Tyrosine kinase ABL JAK2 JAK2 or MPL JAK2 or MPL
Blood ↑WBC with IG, basophils Normo or hypochromatic anemia, may have ↑platelets & basophils Leukoerythroblastic with teardrops ↑Platelets, often abnormal
Marrow ↑↑Myeloids Panmyelosis, ± erythroid hyperplasia, atypical megas Panmyelosis, atypical megas ↑↑Megas
Marrow fibrosis Varies ↑In spent phase ↑↑In fibrotic phase Minimal
Splenomegaly ++ ++ +++ ±
Clinical Presentation /Other B symptoms Hypertension, thrombosis, pruritus,↓EPO B symptoms, bleeding, gout Thrombosis, hemorrhage
CML = chronic myeloid leukemia; PV = polycythemia vera; PMF = primary myelofibrosis; ET = essential thrombocythemia; IG = immature granulocytes; Megas = megakaryocytes; EPO = erythropoietin

 

Common Myeloproliferative Neoplasms - Peripheral Blood
  CML PV Cellular Phase PMF ET
RBC Normal or ↓ Normal, ↑ or ↓, may be hypochromatic or polychromatic ↓, teardrop cells Normal or ↓ (iron deficient anemia)
WBC ↑, left shifted, basophilia, eosinophilia, rarely monocytosis Normal or ↑, +/- basophils, (leukoerythroblastic ini fibrotic stage) ↑granulocytes if leukoerythroblastic Normal
Platelets Normal or ↑ Normal or ↑ Normal or ↑ ↑ (>450 x103/μL)
CML = chronic myeloid leukemia; PV = polycythemia vera; PMF = primary myelofibrosis; ET = essential thrombocythemia

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