CD34 and myeloproliferative neoplasm: Additionally, we demonstrated that not only was the percentage of CD34+CCR2+ cells positively correlated with the degree of BM fibrosis in MPNs (a specular finding to what was described by Dunbar et al. for CXCR1/2) but it also proved an accurate diagnostic tool to discriminate among MPN subtypes with different degrees of bone marrow fibrosis.