title: [Utility of the bone marrow biopsy in the diagnosis of essential thrombocytemia].
abstract: BACKGROUND
  The recent discovery of the Janus Kinase 2 (JAK2(V617F)) mutation, an indicator of clonal expansion, has widely modified the diagnostic work-up of myeloproliferative disorders. However, histopathologic criteria of the WHO classification, focused on megakaryocytes abnormalities, have taken a central role in the diagnosis of essential thrombocytemia (ET), particularly to distinguish it from the prefibrotic myelofibrosis (PMF) evolving to a clinic myelofibrosis unlike true ET. The aim of our study is to evaluate inter-observer reproducibility and prognostic implications of these pathological criteria comparing diagnoses with clinical and biological follow-up.
  
  
  METHODS
  Forty-four patients presenting with isolated thrombocytemia were retrospectively evaluated. All patients were initially diagnosed with ET based on the PVSG classification from 1997. The initial bone marrow biopsy specimens were re-evaluated using the Thiele pathological classification: true ET, prefibrotic myelofibrosis (PMF) and early myelofibrosis. Patients were followed for a median of 6 years.
  
  
  RESULTS
  Our population includes three patients with polycythemia vera and 41 patients with true ET. Based on clinical and biological follow-up, diagnoses were changed to idiopathic myelofibrosis in four of six patients with "early" myelofibrosis (66.7%), but in only one of 14 patients with PMF (7.15%). In contrast, the diagnosis of true ET was not changed in the 21 cases. Inter-observer reproducibility for pathological classification was 100%.
  
  
  CONCLUSIONS
  In this study, our diagnostic methodology based on the clinico-biological follow-up, which has not been evaluated in previous studies, calls into question the diagnostic value of the pathological criteria in PMF.
authors: Hôpital Haut-Lévêque, service de médecine interne, 3604 Pessac, France.
authors: Olivier
authors: O
authors: Rager
authors: Marie
authors: M
authors: Parrens
authors: Josette
authors: J
authors: Brière
authors: Eric
authors: E
authors: Lippert
authors: Noël
authors: N
authors: Milpied
authors: Jean-Luc
authors: JL
authors: Pellegrin
authors: Jean-François
authors: JF
authors: Viallard
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy; D001853:Bone Marrow / Q000473:pathology*; D004252:DNA Mutational Analysis; D005260:Female; D005500:Follow-Up Studies; D006403:Hematologic Tests / Q000379:methods / Q000706:statistics & numerical data; D006801:Humans; D053614:Janus Kinase 2 / Q000032:analysis / Q000235:genetics; D008297:Male; D008875:Middle Aged; D020125:Mutation, Missense; D057089:Pathology, Molecular; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D013920:Thrombocythemia, Essential / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology
chemical_list: C507924:JAK2 protein, human; D053614:Janus Kinase 2