Essential Thrombocythemia

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

A patient must meet 4 major criteria:
Major Criteria :

1. Platelet Count ≥ 450 x 109 / l
2. Both of the following:
   1. Megakaryocyte proliferation with large and mature morphology
   2. No or little granulocyte or erythroid proliferation
3. Not meeting WHO criteria for CML, PV, PMF, MDS or other myeloid neoplasm.
4. One of the following:
   1. Demonstration of the JAK2 V617F mutation
   2. Demonstration of a other clonal marker
   3. No evidence of reactive thrombocytosis

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.