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Bone marrow histology in CALR mutated thrombocythemia and myelofibrosis: Results from two cross sectional studies in 70 newly diagnosed JAK2/MPL wild type thrombocythemia patients

Published on: 21st June, 2019

OCLC Number/Unique Identifier: 8180078896

The clinical phenotypes in 268 JAK2V617F mutated MPN patients in the Seoul study were PV in 101, ET in 95 and MF in 78 and 56 CALR mutated MPN consisted of PV in none, ET in 40 and MF in 16 cases. CALR mutated MPN patients were younger than JAK2V617F mutated MPN patients (mean ages 57.5 and 66 years), had lower values for values for leukocytes (8.6 vs 11.9x109/L) and higher values for platelets (898 vs 643x109/L respectively). Bone marrow histopathology in 268 JAK2V617F mutated MPN patients in the Seoul study was featured by an increased erythropoiesis and megakaryopoiesis (EM) in 13.5%, an increased erythropoiesis, megakaryopoiesis and granulopoiesis (EMG) in 31.3%, a normocellular megakaryocytic (M) proliferation in 29,1%, a megakaryocytic and granulocytic (MG) proliferation with a relative reduction of erythropoiesis in post-ET and Post-PV myelofibrosis in 26.2%. The bone marrow histology in 56 cases of CALR mutated MPN show a predominantly increased megakaryopoiesis (M) in two thirds and an increased megakaryopoiesis and granulopoiesis (MG) with a decreased erythropoiesis in one third. Thirteen consecutive CALR MPN patients in the Belgian & Dutch cross sectional study presented with thrombocythemia associated with a typical PMGM bone marrow histology in 11 and myelofibrosis in 2 cases. All 11 thrombocythemia and 2 myelofibrosis CALR mutated MPN patients did not have constitutional symptoms and did not suffer from microvascular erythromelalgic disturbances, major thrombosis at platelet counts between 400 and 1000x109/L. There was an occurrence of hemorrhages at platelet counts above 1000x109/L in two CALR thrombocythemia cases. Bone marrow histology of CALR mutated thrombocythemia in the Seoul and Belgian/Dutch study showed loose clusters of large megakaryocytes (M) with bulky, cloud-like nuclei with a normal or a minor reduction of erythropoiesis and no increase in reticulin fibers grade 0 or 1 (RF 0 or 1). CALR thrombocythemia patients show various degrees of increased bone marrow cellularity due to dual megakaryocytic and granulocytic (MG) proliferation featured by large megakaryocytes with roundish bulky nuclear forms and cloud-like clumsy nuclei, which are almost never seen in JAK2V617F ET and PV. Assessment of allele burden is an independent and most important factor for all molecular variants MPN disease burden. Overt myelofibrosis with advanced post PV and or ET myelofibrosis at the bone marrow level occurred in one third (30%) of 208 evaluable JAK2 MPN patients and in 8 (14%) of 56 CALR MPN patients in the Seoul study.
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Novel European Asiatic Clinical, Laboratory, Molecular and Pathobiological (2015-2020 CLMP) criteria for JAK2V617F trilinear polycythemia vera (PV), JAK2exon12 PV and JAK2V617F, CALR and MPL515 thrombocythemias: From Dameshek to Constantinescu-Vainchenker, Kralovics and Michiels

Published on: 3rd April, 2020

OCLC Number/Unique Identifier: 8576367174

The Myeloproliferative Neoplasms (MPN) of trilinear polycythemia vera (PV) and megakaryocytic leukemia (ML = primary megakaryocytic granulocytic myeloproliferation: PMGM) and Essential Thrombocythemia (ET) in the studies of Dameshek and Michiels are caused by the MPN driver mutations JAK2V617F, JAK2exon12, CALR and MPL515 discovered by Constantinescu-Vainchenker, Green and Kralovics. The JAK2V617F mutated trilinear myeloproliferative neoplasms (MPN) include a broad spectrum of clinical laboratory and bone marrow features in essential thrombocythemia (ET), prodromal PV and erythrocythemic PV, classical PV and advanced stages of masked PV and PV complicated by splenomegaly and secondary myelofibrosis (MF). Heterozygous JAK2V617F mutated ET is associated with low JAK2 allele and MPN disease burden and normal life expectance. In combined heterozygous and homozygous or homozygous JAK2V617F mutated trilinear PV, the JAK2 mutation load increases from less than 50% in prodromal PV and classical PV to above 50% up to 100% in hypercellular PV, advanced PV and PV with MF. Bone marrow histology show diagnostic features of eryhrocytic, megakaryocytic and granulocytic (EMG) myeloproliferation in JAK2V617F mutated trilinear MPN, which clearly differs from monolinear megakaryocytic (M) myelproliferation in MPL and CALR thrombocythemia and dual megakaryocytic granulocytic (MG) myeloproliferation in CALR mutated thrombocythemia. The morphology of clustered large pleomorphic megakaryocytes with hyperlobulated nuclei are similar in JAK2V617F thrombocythemia, prodromal PV and classical PV patients. Monolinear megakaryocytic (M) myeloproliferation of large to giant megakaryocytes with hyperlobulated staghorn-like nuclei is the hallmark of MPL515 mutated normocellular thrombocythemia. CALR mutated thrombocythemia usually presents with high platelet count around 1000x109/l and normocellular megakaryocytic (M) proliferation of immature megakaryocytes with cloud-like hyperchromatic nuclei followed by dual megakaryocytic granulocytic (MG) myeloproliferation followed by various degrees of bone marrow fibrosis. Natural history and life expectancy of MPN patients are related to the response to treatment and the degree of anemia, splenomegaly, myelofibrosis and constitutional symptoms. The acquisition of epigenetic mutations at increasing age on top of MPN disease burden independently predict unfavorable outcome in JAK2V617F, MPL515 and CALR mutated myeloproliferative neoplasms (MPNs, which mutually exclude each other).
Cite this ArticleCrossMarkPublonsHarvard Library HOLLISGrowKudosResearchGateBase SearchOAI PMHAcademic MicrosoftScilitSemantic ScholarUniversite de ParisUW LibrariesSJSU King LibrarySJSU King LibraryNUS LibraryMcGillDET KGL BIBLiOTEKJCU DiscoveryUniversidad De LimaWorldCatVU on WorldCat