Megakaryocytic morphology in Janus kinase 2 V617F positive myeloproliferative neoplasm

CONTEXT: Alterations in megakaryocyte morphology are the hallmark of myeloproliferative neoplasms (MPNs). These neoplasm are also associated with Janus kinase 2 (JAK2) V617F mutation in nearly 95% patients with polycythemia vera (PV), 40% patients of essential thrombocythemia (ET) and 50% patients of myelofibrosis (MF). The utility of megakaryocyte morphology in these disorders in correlation with JAK2 V617F remains unresolved. AIMS: The aim of the study was to assess the morphology of megakaryocytes in bone marrow aspirates (BMAs) and bone marrow biopsies of patients of BCR-ABL negative MPNs with JAK2 V617F mutation. SETTINGS AND DESIGN: This study was a retrospective and prospective, hospital-based study undertaken for a period ranging from January 2011 to April 2015. SUBJECTS AND METHODS: Assessment of morphological features of megakaryocytes in 15 BMAs and their respective biopsies which included seven cases of PV, three cases of ET, and five cases of MF with JAK2 V617F mutation. STATISTICAL ANALYSIS USED: Chi-square test and Fisher exact test were used to compare the different features of megakaryocytes. Software version SPSS 13.0 was used. RESULTS: Megakaryocytes in ET were found to have characteristically large size with staghorn multinucleated nuclei and exhibiting large amount of cytoplasm. MF showed dense clustering of megakaryocytes with staghorn nucleus along with sinusoidal dilatation and intrasinusoidal hematopoiesis. PV showed loose and dense clustering of megakaryocytes with a predominance of cloud-like nuclei. Few of the megakaryocytic morphologic features showed overlap between MF and PV and between ET and early MF. CONCLUSIONS: Megakaryocytic morphology can aid in the accurate diagnosis of the different subcategories of MPNs. This would help in categorization of clinically suspicious patients of JAK2 V617F negative patients.