Myelofibrotic transformations of polycythemia vera and essential thrombocythemia are morphologically biologically and prognostically indistinguishable from primary myelofibrosis

摘要

A fraction of polycythemia vera (PV) & essential thrombocythemia (ET) cases will, in time, undergo myelofibrotic transformation. In such cases, fibrosis may mask the diagnostic histological features of the original underlying myeloproliferative neoplasm (MPN). Thus confidently differentiating postfibrotic PV/ET from primary myelofibrosis (PMF) histologically may not be possible.It is controversial whether post PV/ET myelofibrosis (MF) differs clinicopathologically from PMF, or if these entities are biologically, clinically, and prognostically indistinguishable. To answer this question, we compared multiple candidate biologic, morphologic, and prognostic parameters between 19 postfibrotic ET/PV individuals and 18 PMF individuals. The postfibrotic ET/PV and PMF cases did not differ in regards to clinical outcome, cytogenetic abnormalities, serum lactate dehydrogenase (LDH) level, peripheral blast count, bone marrow morphology, or grade of reticulin fibrosis. Only JAK2 allele burden differed between the two groups, which was higher in the postfibrotic PV/ET population (p=0.011).Cardinal morphologic features of PMF (i.e. marrow cellularity, intrasinusoidal hematopoiesis, osteosclerosis, etc.) were commonly observed in post-PV/ET MF marrow biopsies and only a minority of post-PV/ET MF marrow biopsies retained diagnostic features of the primary MPN (panmyelosis in PV and megakaryocytic hyperplasia in ET). Our study indicates that PMF and post-PV/ET MF are clinically and biologically indistinguishable.