Table 1.

MF diagnostic criteria

Criteria for PMF*
Major criteria
    1Megakaryocyte proliferation and atypical morphology, typically accompanied by bone marrow fibrosis (i.e., increased collagen or reticulin staining)
    2Does not meet WHO criteria for PV, chronic myelogenous leukemia, myelodysplastic syndrome, or other myeloid neoplasm
    3Presence of JAK2 V617F or other clonal marker (e.g., MPL W515L>K)
Minor criteria
    2Serum level of lactate dehydrogenase increased**
    4Palpable splenomegaly**
  • *Revised WHO criteria for PMF modified from (13); diagnosis requires meeting all 3 major criteria and 2 minor criteria.

  • Dense clustered megakaryocytes with abnormally increased nuclear/cytoplasmic ratio and hyperchromatic and round or irregularly folded nuclei. In the absence of overt reticulin fibrosis, increased megakaryocyte proliferation must be accompanied by granulocyte proliferation, with or without erythropoiesis.

  • In the absence of significant reticulin fibrosis, the megakaryocyte changes must be accompanied by an increased bone marrow cellularity characterized by granulocytic proliferation and often decreased erythropoiesis.

  • In the absence of clonal marker, it requires that bone marrow fibrosis not be secondary to infection, inflammation, exposure to toxic agents, or autoimmune response, or the presence of hematologic (e.g., lymphoma, hairy cell leukemia) or metastatic malignancy.

  • **May present as borderline to marked abnormality.