Blood Res 2021; 56(1): 4-4
Circulating megakaryocyte in primary myelofibrosis: an uncommon finding in a myelofibrosis blood smear
Pedro Asensi Cantó, María Leonor Senent Peris, Elvira Mora Casterá
Department of Haematology, Hospital La Fe, Valencia, Spain
Correspondence to: Pedro Asensi Cantó, M.D., Department of Hematology, Hospital La Fe, Av. De Fernando Abril Martorell, Valencia 106-46026, Spain, E-mail:
Received: October 28, 2020; Revised: November 22, 2020; Accepted: January 19, 2021; Published online: February 5, 2021.
© The Korean Journal of Hematology. All rights reserved.

cc This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

A 57-year-old man diagnosed with JAK2+ prefibrotic/early primary myelofibrosis (MF) progressed during the one-year follow-up to the overt fibrotic stage (A, reticulin stain, ×100 and B, Masson’s trichrome stain, ×100). Complete blood count showed no cytopenia (hemoglobin 14.4 g/dL, 12.79×109 leukocytes/L, and 148×109 platelets/L). Initial blood-smear examination with low amplification objectives (C, Giemsa stain, ×200) showed the leukoerythroblastic morphology frequently seen in MF, with circulating myeloid precursors, erythroblasts, and anisopoikilocytosis. Surprisingly, a megakaryocyte was found in the body of the slide. Higher amplification (D, Giemsa stain, ×600) enabled better characterization of this atypical small megakaryocyte with a non-lobated nucleus. Isolated (bare or naked) megakaryocyte nuclei are typical findings in MF. Intact megakaryocytes have rarely been reported in peripheral blood smears. If present, the feathered edge of the smear is the predilected location of these cells as they are among the largest cells in the sample and tend to be dragged when extending the sample, whereby their morphology may be altered. This finding emphasizes the importance of a systemic approach to blood-smear examination, starting scanning at low magnification for full coverage of the sample and identification of the best regions for higher magnification.


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