Table 3
WHO diagnostic criteria for PMF requires meeting all 3 major criteria and ≥ 2 minor criteria outlined30  

  • Major criteria

    • Megakaryocyte proliferation, including small-to-large megakaryocytes, with aberrant nuclear/cytoplasmic ratio and hyperchromatic and irregularly folded nuclei and dense clustering accompanied by either reticulin and/or collagen fibrosis, or in the absence of reticulin fibrosis (ie, prefibrotic PMF), the megakaryocyte changes must be accompanied by increased marrow cellularity, granulocytic proliferation, and often decreased erythropoiesis (Figure 1).

    • Not meeting WHO criteria for chronic myelogenous leukemia, polycythemia vera, myelodysplastic syndromes, or other myeloid neoplasm

    • Demonstration of JAK2V617F or other clonal marker or no evidence of reactive marrow fibrosis

  • Minor criteria

    • Leukoerythroblastosis

    • Increased serum lactate dehydrogenase

    • Anemia

    • Palpable splenomegaly

 
International Working Group for Myeloproliferative Neoplasms Research and Treatment criteria for post-polycythemia vera/essential thrombocythemia (post-PV/ET) myelofibrosis requires meeting both major criteria and ≥ 2 minor criteria3  

  • Major criteria

    • Documentation of a previous diagnosis of PV or ET as defined by the WHO criteria

    • Bone marrow fibrosis grade 2-3 (on 0-3 scale) or grade 3-4 (on 0-4 scale)*

  • Minor criteria

    • A leukoerythroblastic peripheral blood picture (for both PV and ET)

    • Increasing splenomegaly defined as either an increase in palpable splenomegaly of ≥ 5 cm (distance of the tip of the spleen from the left costal margin) or the appearance of a newly palpable splenomegaly (for both PV and ET)

    • Development of ≥ 1 of 3 constitutional symptoms: > 10% weight loss in 6 months, night sweats, unexplained fever (> 37.5°C) (for both PV and ET)

    • Anemia or sustained loss of requirement for phlebotomy in the absence of cytoreductive therapy (for PV)

    • Anemia and a decrease of hemoglobin level ≥ 2 g/dL from baseline (for ET)

    • Increased serum lactate dehydrogenase (for ET)

 
WHO diagnostic criteria for PMF requires meeting all 3 major criteria and ≥ 2 minor criteria outlined30  

  • Major criteria

    • Megakaryocyte proliferation, including small-to-large megakaryocytes, with aberrant nuclear/cytoplasmic ratio and hyperchromatic and irregularly folded nuclei and dense clustering accompanied by either reticulin and/or collagen fibrosis, or in the absence of reticulin fibrosis (ie, prefibrotic PMF), the megakaryocyte changes must be accompanied by increased marrow cellularity, granulocytic proliferation, and often decreased erythropoiesis (Figure 1).

    • Not meeting WHO criteria for chronic myelogenous leukemia, polycythemia vera, myelodysplastic syndromes, or other myeloid neoplasm

    • Demonstration of JAK2V617F or other clonal marker or no evidence of reactive marrow fibrosis

  • Minor criteria

    • Leukoerythroblastosis

    • Increased serum lactate dehydrogenase

    • Anemia

    • Palpable splenomegaly

 
International Working Group for Myeloproliferative Neoplasms Research and Treatment criteria for post-polycythemia vera/essential thrombocythemia (post-PV/ET) myelofibrosis requires meeting both major criteria and ≥ 2 minor criteria3  

  • Major criteria

    • Documentation of a previous diagnosis of PV or ET as defined by the WHO criteria

    • Bone marrow fibrosis grade 2-3 (on 0-3 scale) or grade 3-4 (on 0-4 scale)*

  • Minor criteria

    • A leukoerythroblastic peripheral blood picture (for both PV and ET)

    • Increasing splenomegaly defined as either an increase in palpable splenomegaly of ≥ 5 cm (distance of the tip of the spleen from the left costal margin) or the appearance of a newly palpable splenomegaly (for both PV and ET)

    • Development of ≥ 1 of 3 constitutional symptoms: > 10% weight loss in 6 months, night sweats, unexplained fever (> 37.5°C) (for both PV and ET)

    • Anemia or sustained loss of requirement for phlebotomy in the absence of cytoreductive therapy (for PV)

    • Anemia and a decrease of hemoglobin level ≥ 2 g/dL from baseline (for ET)

    • Increased serum lactate dehydrogenase (for ET)

 
*

Grade 2-3 according to the European classification97 : diffuse, often coarse fiber network with no evidence of collagenization (negative trichrome stain) or diffuse, coarse fiber network with areas of collagenization (positive trichrome stain). Grade 3-4 according to the standard classification98 : diffuse and dense increase in reticulin with extensive intersections, occasionally with only focal bundles of collagen and/or focal osteosclerosis or diffuse and dense increase in reticulin with extensive intersections with coarse bundles of collagen, often associated with significant osteosclerosis.

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