The Morphology Character Of Bone Marrow In The Prefibrotic-early Primary Myelofibrosis

Background:BCR-ABL(-) myeloproliferative neoplasms(MPN) mainly included polycythaemia vera(PV), essential thrombocythaemia(ET) and primary myelofibrosis(PMF). In the revised WHO diagnostic standard, JAK2V617F mutaion was added as a reference. It was reported that the JAK2V617F mutaion was detected about in 90% PV,50% ET and 50%PMF. It played a critical role in distinguishing BCR-ABL(-) MPN from other haematological diseases. While to PV, ET and PMF, BM morphology was the still the main way in distinguishing from each other. As to prefibrotic-early PMF and ET, they both have similar clinical presentation, while contrast to ture ET, prefibrotic-early PMF show progression to overt myelofibrosis easily. So it was very important to distinguish from each other. In our study,156 cases labeled as uncertain ET with BM aspirate smears, trephine biopsy sections and imprints conducted simultaneously were recruited, and the BM morphologic character between the prefibrotic-early PMF and ET groups were analyzed.Materials and methods:BM aspirate smears, trephine biopsy sections and imprints were taken and processed in our bone marrow (BM) room. JAK2V617F mutation was tested by wu han hai si te kang sheng da company.As prefibrotic-early PMF show progression to overt myelofibrosis easily, Based on this character,7 cases treated with aspirin or interferon progressed to overt myelofibrosis within five years were selected as prefibrotic-early PMF, the morphology of which was analyzed. Based on the WHO standard,156 cases of uncertain ET with BM aspirate smears, trephine biopsy sections and imprints conducted simultaneously were reclassified, the BM morphologic character between the prefibrotic-early PMF and ET groups were analyzed. In addition,22 cases of prefibrotic-early PMF and 27 ET were selected for morphological comparison between the JAK2V617F mutation positive and negative groups.Results:To the seven cases of prefibrotic-early PMF, clusters of megakaryocyte and platelet were found in the BM smear. As to the BM imprint, nucleated cells (granulocytes) were increased in these seven cases, clusters of megakaryocytes were easily found. Granules in the background of BM imprint were obviouly increased in one case. Of the BM section, megakaryocytic cluster with various size, cloud-like megakaryocyte, large ball-like megakaryocyte, increased nucleated cells (granulocyte), small bare nucleus, megakaryocyte near bone trabecula, and compact megakaryocytic cluster could all be found in seven cases, and giant deeply lobulated megakaryocyte was found in three cases.Of the 156 cases of uncertain ET, it was reclassified as 27 cases of MF-1,12 PMF and 83 ET. The platelet count and LDH level in MF-1 group were obviously higher than ET group (P＜0.05). The blast percentage of BM smear in MF-1 group was also higher than ET group (P<0.05). As to BM section, cases with increased nucleated cells (granulocyte), compact megakaryocytic cluster, megakaryocyte near bone trabecula, cloud-like megakaryocyte, small bare nucleus of megakaryocyte, and large ball-like megakaryocyte in MF-0 and MF-1 group were significantly higher than ET group (all P＜0.05), cases with megakaryocytic cluster of various size in MF-1 group were significantly higher than MF-0 and ET groups(P<0.05). The JAK2V617F mutation rate in prefibrotic-early PMF and ET groups were 54.5% and 48.1%, respectively. Hb level in JAK2V617F mutation positive group was obviously higher than the negative group (P<0.05), no special change with megakaryocytic morphology was found between the positive and negative groups.Discussion:1. The morphologic character of BM section, especially megakaryocytic morphology, paly an important role in distinguishing prefibrotic-early PMF from ET.2. The importance of morphologic index in distinguishing prefibrotic-early PMF from ET were megakaryocytic cluster with various size, cloud-like megakaryocyte, large ball-like megakaryocyte, increased nucleated cells (granulocyte), small bare nucleus, megakaryocyte near bone trabecula and compact megakaryocytic cluster in order.3. JAK2V617F mutation has no special impact to the megakaryocytic morphology, but it could enhance the hematopoiesis of BM nucleated erythrocytes..