Pilot Study for the Development of a Diagnostic Score to Differentiate Myeloproliferative Neoplasms.

The diagnostic criteria for myeloproliferative neoplasia have recently been revised in the WHO 2016 classification, which now recognizes a new entity between essential thrombocythemia (TE) and overt myelofibrosis (or primary myelofibrosis): prefibrotic myelofibrosis. Prefibrotic myelofibrosis patients seem to have a poorer prognosis compared to essential thrombocythemia in term of overall survival and myelofibrotic evolution. The dichotomy between these diseases is based on the bone marrow biopsy evaluation and is challenging with a lack of reproducibility showed in the literature. This study aims to develop a diagnostic non-invasive score for differentiating prefibrotic myelofibrosis from essential thrombocytosis and overt myelofibrosis. The parameters studied are : * spleen fibrosis by elastography * plasma cytokines levels * mutationnal landscape by NGS * CD34 circulating cells Bone marrow biopsy were reviewed by 2 anatomopathologists. Number of patients to be enrolled : 130