Proliferative characteristics of Philadelphia‐negative myeloproliferative neoplasms ‐ clinical implications

Summary Introduction Philadelphia‐negative myeloproliferative neoplasms (Ph − MPN ) are characterized by overproduction of one or more blood cell lines. Methods We studied the proliferative characteristics of 91 patients with de novo Ph − MPN . Colony‐forming cells ( CFC ) and endogenous colonies ( EC ), from bone marrow ( BM ) and/or peripheral blood ( PB ), were analyzed by colony assay based on methylcellulose. The level of circulating CD 34 + cells was determined by flow cytometry. Results The total number of PB CFC in primary myelofibrosis ( PMF ) was increased compared to the control sample ( P < 0.01) and essential thrombocythemia ( ET ) ( P < 0.05). The highest number of BM and PB EC was observed in polycythemia vera ( PV ) ( P < 0.01). Increased levels of CD 34 + cells characterized early‐prefibrotic (57%) and advanced‐fibrotic PMF (90%) as compared to PV (34%) and ET (32%) ( P < 0.01). In the whole Ph − MPN group, the total number of PB CFC ( P < 0.01), PB EC ( P < 0.05), and CD 34 + cells ( P < 0.01) correlated with the degree of BM fibrosis. Higher levels of circulating CD 34 + cells in PMF correlated with the total number of PB EC ( P < 0.05) and degree of BM fibrosis ( P < 0.01). Conclusions Exploration of the PB proliferative characteristics of Ph − MPN on diagnosis may be helpful in revealing early‐prefibrotic PMF . Monitoring the levels of circulating CD 34 + cells may provide a sensitive indicator of fibrotic evolution in PV and PMF .