OBJECTIVETo investigate the significance of clinicopathological stage of chronic idiopathic myelofibrosis (CIMF) in WHO classification of 2001.

METHODSHistopathological analysis of bone marrow biopsy plastic-embedded sections stained with H-G-E and Gomori's stains and clinical features of 113 cases previously diagnosed as primary myelofibrosis (PMF) and 48 cases MPD-U (total of 161 cases which including male 79 and female 82) were studied retrospectively.

RESULTSThere was no significant differences on the clinical features among the cellular phase, collagen fiber phase, sclerotic phase and osteomyelosclerosis of 113 previously diagnosed patients. According to WHO classification 2001 of CIMF, previously diagnosis in 48 cases with MPD-U was WHO pre-CIMF, and in 113 cases with PMF was WHO CIMF-Fs. There were significant differences between of WHO pre-CIMF and WHO CIMF-Fs about clinicopathological features except age. The percentage of immature granulocytes, normoblasts, lymphocytes in peripheral blood, the size of hepatosplenomegaly, and the percent age of tear drop-like red blood cells in pre-CIMF were significantly lower than those in CIMF-Fs (P < 0.05). However, the number of hemoglobin and platelets in patients with pre-CIMF were significantly higher than that with CIMF-Fs (P < 0.01).

CONCLUSIONpre-CIMF and CIMF-Fs in clinical and histopathological features were different development stage of CIMF, while osteomyelosclerosis is a variant of CIMF, but not an independent disease.