Prodromal myeloproliferative neoplasms: the 2008 WHO classification.

The concept of prodromal chronic myeloproliferative neoplasms has been endorsed by the WHO classification implicating a stepwise evolution of disease. Histology of the bone marrow (BM) and borderline to mildly expressed clinical features play a pivotal role for diagnosing prefibrotic-early primary myelofibrosis. By lowering the platelet count for essential thrombocythemia and regarding BM morphology, early manifestations are tackled. Pre-polycythemic stages of polycythemia vera with a low hemoglobin level at onset are diagnosed by positive JAK2V617F mutation status, a low erythropoietin value, and characteristic BM features. The revised WHO classification incorporates hematological, morphological, and molecular-genetic parameters to generate a consensus-based working diagnosis.