• Nataliya Vytrva, Elvira Stacher, Peter Regitnig, Wilma Zinke-Cerwenka, Sabine Hojas, Eva Hubmann, Anna Porwit, Magnus Bjorkholm, Gerald Hoefler, and Christine Beham-Schmid.
• From the Institute of Pathology (Drs Vytrva, Stacher, Regitnig, Hoefler, and Beham-Schmid) and the Division of Hematology, Department of Medicine (Dr Zinke-Cerwenka), Medical University of Graz, Graz, Austria; the Division of Hematology, Department of Medicine, General Hospital Fürstenfeld, Fürstenfeld, Austria (Dr Hojas); the Division of Hematology, Department of Medicine, General Hospital Leoben, Leoben, Austria (Dr Hubmann); and the Department of Pathology, Radiumhemmet (Dr Porwit), and the Division of Hematology, Department of Medicine (Dr Bjorkholm), Karolinska University Hospital, Stockholm, Sweden. Dr Vytrva is now with the Department of Clinical Pathology, Ryhov Hospital, Jönköping, Sweden. Dr Porwit is now with the Department of Laboratory Hematology, General Hospital of Toronto, Toronto, Ontario, Canada. Drs Vytrva and Stacher contributed equally to the study.
• Arch. Pathol. Lab. Med. 2014 Sep 1;138(9):1203-9.

ContextMegakaryocytes are the "hallmark" of Philadelphia chromosome-negative myeloproliferative neoplasms, such as essential thrombocythemia, polycythemia vera, and primary myelofibrosis; their morphology in correlation with Janus kinase 2 (JAK2 V617F) mutation as well as clinical and laboratory parameters remains unknown.ObjectiveTo assess the morphology of megakaryocytes in bone marrow biopsies of patients with and without JAK2 V617F mutation.DesignAssessment of morphologic features of megakaryocytes in 112 bone marrow biopsies (52 essential thrombocythemia, 38 polycythemia vera, and 22 primary myelofibrosis) and correlation with clinical and laboratory data.ResultsJAK2 V617F mutation was detected in 24 of 52 essential thrombocythemia cases (46.2%), 36 of 38 polycythemia vera cases (97.5%), and 14 of 22 primary myelofibrosis cases (63.6%). By investigating morphometric and clinical parameters using multivariate analysis, we found that higher hemoglobin concentration, higher white blood cell counts, and lower platelet counts were significantly associated with JAK2 V617F. Striking morphologic similarities were found between polycythemia vera JAK2 V617F and primary myelofibrosis JAK2 V617F concerning the localization and cytoplasmic size of megakaryocytes. Although polycythemia vera JAK2 V617F and essential thrombocythemia JAK2 V617F shared similarities in localization, distribution, and amount of megakaryocytes, morphology was different. Megakaryocytic morphology also differed between primary myelofibrosis JAK2 V617F and essential thrombocythemia JAK2 V617F.ConclusionOur results indicate that primary myelofibrosis JAK2 V617F and polycythemia vera JAK2 V617F share pathogenetic pathways, resulting in morphologically similar megakaryocytes.

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