primary myelofibrosis


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  • Clinical

    • anemia, leukocytosis, thrombocytosis
    • splenomegaly
    • CD34+ cells in blood (later stages)
    • increased LDH
    • leukoerythroblastosis

  • Criteria

    • 3/3 major
      • atypical megakaryocyte proliferation with fibrosis (reticulin or collagen) or prefibrosis (hypercellular, granulocytic proliferation, decreased erythropoiesis)
      • rule out other myeloid neoplasms (PCV, CML, MDS)
      • is clonal (JAK2 or MPL) or rule out inflammatory, HCL, lymphoid etiologies
    • 2/4 minor
      • leukoerythroblastosis
      • increased LDH
      • anemia
      • splenomegaly

  • Stages

    • prefibrotic
      • blood: thrombocytosis, mild anemia
      • hypercellular marrow
      • Atypical megakaryocytes proliferation
        • clustering
        • enlarged
        • nuclear atypia: plump lobation (cloud-like), hyperchromasia, clumpy chromatin
      • granulocyte proliferation
      • mild decrease in erythropoiesis
    • fibrotic
      • blood: teardrop cells (anisopoikilocytosis), anemia, leukoerythroblastosis
      • fibrosis: reticulin -> collagen -> osteosclerosis
      • osteosclerosis: broad irregular trabeculae
      • hypocellular marrow (can be focally normocellular)
      • atypical megakaryocytes
      • proliferation of vessels
    • accelerated: previous PMF, now with 10-19% blasts (PB or BM) and increased CD34+ cells
    • transformed: previous PMF, now with 20% blasts

  • Grading

    • MF0: scattered reticulin, no intersections (normal marrow)
    • MF1: loose reticulin, many intersections
    • MF2: dense diffuse reticulin, extensive intersections
    • MF3: collagen, osteosclerosis

  • Molecular

    • JAK2 V617F in 50%
    • CALR in 30% of JAK2 negative cases
    • MPL W515K/L in 5%
    • del(13)(q12-22)
    • der(6)t(1;6)(q21-23;p21.3)
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