Myeloproliferative Neoplasms (MPNs) are clonal hematopoietic stem disorders characterized by high rate of effective proliferation of one or more cell lineage. MPNs are overlapping syndromes that can progress to fibrotic stage or evolute into acute leukemia. Preliminary results of a pilot study (5) suggested that this technique could be useful to assess bone marrow (BM) activity and extramedullary hematopoiesis in patients with Myelofibrosis (MF).