Abstract
The classifications of Myeloproliferative Disorders (MPD) by the Polycythemia Vera Study Group (PVSG) and World Health Organization (WHO) used crude criteria for the diagnoses of Essential Thrombocythemia (ET), Polycythemia Vera (PV) and Primary Myelo Fibrosis (PMF). The PVSG and the 2007 WHO criteria for the diagnosis of ET and PVoverlook the very early prefibrotic stages of MPN. The 2008 European Clinical, Molecular and Pathological (2008 ECMP) criteria are sensitive for the detection of early stages of JAK2 V617F trilinear Myelo Proliferative Neoplasms (MPN) and could delineate three stages JAK2 V617F mutated ET: normocellular ET; ET with features of early PV (prodromal PV); and ET with Hypercellular Megakaryocytic Granulocytic Myeloproliferation (EMGM). The 2008 ECMP classification distinguishes six clinical PV stages that have important prognostic and therapeutic implications. Spontaneous EEC, low serum erythropoietin (EPO) levels and JAK2 mutations are highly specific for ET with PV features (prodromal PV), masked PV and classical PV. JAK2 wild type ET and MF have no blood and bone marrow features of PV. The detection and quantitation of JAK2 V617F mutation allele burden play a key-role in the diagnostic work-up and staging of ET, PV and MF patients. The JAK2 V617F mutation allele burden in heterozygous mutated ET and in combined heterozygous-homozygous or homozygous mutated PV and EMGM is of major clinical and prognostic significance. Pre-treatment bone marrow histopathology is of huge importance to document and stage the broad spectrum JAK2 mutated and JAK wild type MPN. JAK2 wild type ET carrying the MPL 515 mutation is a separate and distinct MPN entity of ET and MF without features of PV at diagnosis and during follow-up. JAK2 wild type hypercellular ET associated with Primary Megakaryocytic Granulocytic Myeloproliferation (PMGM) is the third MPN entity of elusive etiology. Myelofibrosis (MF) is not a primary MPN disease entity because Reticulin Fibrosis (RF) and Reticulin/Collagen Fibrosis (RCF) are a secondary response of polyclonal fibroblasts to cytokines released from the clonal granulocytic and megakaryocytic proliferative cells.
Highlights
In the 19th century Chronic Myeloid Leukemia (CML) and Polycythemia Vera (PV) have been described as primary distinct disease entities [1,2,3]
Lumping erythroleukemia with PV, and putting together Chronic granulocytic or Myeloid Leukemia (CML) with PV appeared to be without scientific foundation (Figure 1)
Simple tests like blood cell counts including platelets, leukocytes, hematocrit and erythrocytes above 6x1012/L40, and spleen size on echogram are not taken into account to distinguish the early thrombocythemic and erythrocythemic stages of PV from the classical overt trilinear polycythemic stage of classic PV as documented by bone marrow biopsy showing typical erythroid, granulocytic and megakaryocytic myeloproliferation [46,47]
Summary
In the 19th century Chronic Myeloid Leukemia (CML) and Polycythemia Vera (PV) have been described as primary distinct disease entities [1,2,3]. Simple tests like blood cell counts including platelets, leukocytes, hematocrit and erythrocytes above 6x1012/L40, and spleen size on echogram are not taken into account to distinguish the early thrombocythemic and erythrocythemic stages of PV from the classical overt trilinear polycythemic stage of classic PV as documented by bone marrow biopsy showing typical erythroid, granulocytic and megakaryocytic myeloproliferation [46,47].
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