Primary Myelofibrosis

The World Health Organization (WHO) classification of myeloproliferative neoplasms (MPN)[1,2] was revised in 2008 and defines the diagnosis of Primary Myelofibrosis (PMF) according to the following algorithm:

A patient must meet all 3 major criteria and 2 minor criteria:
Major Criteria:

1. Megakaryocyte proliferation and atypia
   1. Atypia: small to large megakaryocytes with an aberrant nuclear/cytoplasmic ratio and hyperchromatic and irregularly folded nuclei and dense clusteringaccompanied by one of the following:
      1. reticulin and / or collagen fibrosis
      2. in the absence of reticulin fibrosis, the megakaryocyte changes must be accompanied by increased bone marrow cellularity, granulocytic proliferation and often decreased erythropoiesis (i.e. prefibrotic PMF).
   2. Not meeting WHO criteria for CML, PV, MDS, or other myeloid neoplasm
   3. One of the following
      1. Demonstration of the JAK2 V617F mutation
      2. Demonstration of a other clonal marker
      3. No evidence of reactive bone marrow fibrosis

Minor Criteria:

1. Leukoerythroblastosis
2. Increased Serum LDH
3. Anemia
4. Palpable Splenomegaly

References

1. Swerdlow S, Campo E, Harris N. WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues. IRAC Press. 2008:Lyon, France.
2. Tefferi A, Thiele J, Vardiman JW. The 2008 World Health Organization classification system for myeloproliferative neoplasms: order out of chaos. Cancer. 2009;115(17):3842-3847
3. Visit also the FIM (French Intergroup MPD) website.