Chronic myeloproliferative disorders (CMPD)

SOHO State of the Art Updates and Next Questions | Diagnosis, Outcomes, and Management of Prefibrotic Myelofibrosis

Prefibrotic primary myelofibrosis (prefibrotic PMF) is a myeloproliferative neoplasm with distinct characteristics comprising histopathological and clinico-biological parameters. It is classified as a subtype of primary myelofibrosis. In clinical practice, it is essential to correctly distinguish prefibrotic PMF from essential thrombocythemia especially but also overt PMF besides other myeloid neoplasms. Risk stratification and survival outcomes for prefibrotic PMF are worse than that of ET but better than that of overt PMF. Rates of progression to overt PMF and blast phase disease are also higher for prefibrotic PMF than ET. In this review we first discuss the historical context to the evolution of prefibrotic PMF as an entity, its presenting features and diagnostic criteria. We emphasize the differences between prefibrotic PMF, ET, and overt PMF with regards to presenting features and disease outcomes including thrombohemorrhagic events and progression to fibrotic and blast phase disease. Next, we discuss the risk stratification models and contextualize these in the setting of clinical management. We share our view of personalizing treatment to address unique patient needs in the context of currently available management options. Lastly, we discuss areas of critical need in clinical research and speculate on the possibility of future disease course modifying therapies in prefibrotic PMF.

The Classification of Myeloproliferative Neoplasms: Rationale, Historical Background and Future Perspectives with Focus on Unclassifiable Cases

Myeloproliferative neoplasms (MPNs) are a heterogeneous group of clonal hematopoietic stem cell disorders, characterized by increased proliferation of one or more myeloid lineages in the bone marrow. The classification and diagnostic criteria of MPNs have undergone relevant changes over the years, reflecting the increased awareness on these conditions and a better understanding of their biological and clinical-pathological features. The current World Health Organization (WHO) Classification acknowledges four main sub-groups of MPNs: (i) Chronic Myeloid Leukemia; (ii) classical Philadelphia-negative MPNs (Polycythemia Vera; Essential Thrombocythemia; Primary Myelofibrosis); (iii) non-classical Philadelphia-negative MPNs (Chronic Neutrophilic Leukemia; Chronic Eosinophilic Leukemia); and (iv) MPNs, unclassifiable (MPN-U). The latter are currently defined as MPNs with clinical-pathological findings not fulfilling the diagnostic criteria for any other entity. The MPN-U spectrum traditionally encompasses early phase MPNs, terminal (i.e., advanced fibrotic) MPNs, and cases associated with inflammatory or neoplastic disorders that obscure the clinical-histological picture. Several lines of evidence and clinical practice suggest the existence of additional myeloid neoplasms that may expand the spectrum of MPN-U. To gain insight into such disorders, this review addresses the history of MPN classification, the evolution of their diagnostic criteria and the complex clinical-pathological and biological features of MPN-U.

Clinical, pathological and molecular features of the chronic myeloproliferative disorders: MPD 2005 and beyond

The combined use of bone marrow histopathology, biomarkers and clinical features has the potential to diagnose, stage and distinguish early and overt stages of ET, PV and idiopathic myelofibrosis, that has an important impact on prognosis and treatment of MPD patients. As the extension of the PVSG and WHO for ET, PV and agnogenic myeloid metaplasia (AMM), a new set of European clinical and pathological (ECP) criteria clearly distinct true ET from early or latent PV mimicking true ET, overt and advanced polycythemia vera (PV), and from thrombocythemia associated with prefibotic, early fibrotic stages of chronic megakaryocytic granulocytic metaplasia (CMGM) or chronic idiopathic myelofibrosis (CIMF). Cases of atypical MPD and masked PV are usually overlooked by clinicians and pathologists. Bone marrow biopsy will not differentiate between post-PV myelofibrosis versus so-called classical agnogenic myeloid metaplasia. The recent discovery of the JAK2 V617F mutation can readily explain the trilinear megakaryocytic, erythroid and granulocytic proliferation in the bone marrow, but also the etiology of the platelet-mediated microvascular thrombotic complications at increased platelet counts and red cell mass in essential thrombocythemia and polycythemia vera.

Clonal Analysis of Agnogenic Myeloid Metaplasia

Agnogenic myeloid metaplasia (AMM) is a chronic myeloproliferative disorder that leads to a sustained proliferation of megakaryocytes and an increase of reticulin fibers within the bone marrow. Blood and bone marrow samples from patients with advanced AMM with fully developed myelofibrosis as well as cases in the cellular phase of the disease were investigated for clonality. Clonality was studied by X-linked restriction length polymorphism in conjunction with DNA methylation patterns. Granulocytes and total bone marrow cells proved to be monoclonal in origin whereas at least a minor portion of the peripheral lymphocytes were not clonally derived. Our findings indicate that the cellular phase of AMM as well as the fully developed disease progressed to myelofibrosis represent a monoclonal proliferation of pluripotent hematopoietic stem cells.

Current diagnostic criteria for the chronic myeloproliferative disorders (MPD) essential thrombocythemia (ET), polycythemia vera (PV) and chronic idiopathic myelofibrosis (CIMF)

The clinical criteria for the diagnosis of essential thrombocythemia (ET) according to the polycythemia vera study group (PVSG) do not distinguish between ET and thrombocythemia associated with early stage PV and prefibrotic chronic idiopathic myelofibrosis (CIMF). The clinical criteria of the PVSG for the diagnosis of polycythemia vera (PV) only detects advanced stage of PV with increased red cell mass. The bone marrow criteria of the World Health Organization (WHO) are defined by pathologists to explicitly define the pathological criteria for the diagnostic differentiation of ET, PV, and prefibrotic and fibrotic CIMF. As the clinical PVSG and the pathological WHO criteria show significant shortcomings, an updated set of European Clinical and Pathological (ECP) criteria combined with currently available biological and molecular markers are proposed to much better distinct true ET from early PV mimicking ET, to distinguish ET from thrombocythemia associated with prefibrotic CIMF, and to define the various clinical and pathological stages of PV and CIMF that has important therapeutic and prognostic implications. Comparing the finding of clustered giant abnormal megakaryocytes in a representative bone marrow as a diagnostic clue to MPD, the sensitivity for the diagnosis of MPD associated with splanchnic vein thrombosis was 63% for increased red cell mass, 52% for low serum EPO level, 72% for EEC, and 74% for splenomegaly indicating the superiority of bone marrow histopathology to detect masked early and overt MPD in this setting. The majority of PV and about half of the ET patients have spontaneous EEC, low serum EPO levels and PRV-1 over-expression and are JAK2 V617F positive. The positive predictive value for the diagnosis of PV of spontaneous growth of endogenous erythroid colonies (EEC) of peripheral blood (PB) and bone marrow (BM) cells is about 80-85% when either PB or BM EEC assays, and up to 94% when BM and PB EEC assays were performed. The diagnostic impact of low serum EPO levels (ELISA assay) in a large study of 186 patients below the normal range (<3.3 IU/l) had a sensitivity specificity and positive predictive value of 87%, 97% and 97.8%, respectively, for the diagnosis of PV. There is a significant overlap of serum EPO levels in PV versus control and controls versus SE. The specificity of a JAK2 V617F PCR test for the diagnosis of MPD is high (near 100%), but only half of ET and MF (50%) and the majority of PV (up to 97%) are JAK2 V617F positive. The use of biological markers including JAK2 V617 PCR test, serum EPO, PRV-1, EEC, leukocyte alkaline phosphatase score and peripheral blood parameters combined with bone marrow histopathology has a high sensitivity and specificity (almost 100%) to diagnose the early and overt stages of ET, PV and CIMF in JAK2 V617F positive and negative MPDs.

Megakaryocyte-bone marrow stromal cell aggregates demonstrate increased colony formation and alkaline phosphatase expression in vitro

Bone marrow stromal cells (BMSCs) possess certain stem celllike properties and can differentiate to adopt a number of mesenchymal phenotypes. BMSCs are usually investigated in vitro as homogeneous single-cell suspensions; however, these preparations lose much of their osteogenic capacity. Using the fibroblastic colony-forming unit assay, we have compared the proliferation and capacity to express alkaline phosphatase of BMSC-containing aggregates of bone marrow cells with single-cell suspensions of bone marrow cells from the same source. Aggregates were separated from single cells by density gradient centrifugation or cell sieving. The aggregate and single-cell preparations gave rise to similar numbers of colonies; however, the colonies produced by the aggregates were larger and expressed higher levels of alkaline phosphatase. When the aggregates were dissociated, colonies still formed; however, they expressed negligible levels of alkaline phosphatase. Immunomagnetic selection and immunofluorescent staining for CD61, N-methyl-D-aspartate (NMDA) receptor subunit 1, and acetylcholinesterase showed that the majority of the aggregates giving rise to osteoblastic colonies contained megakaryocytes. These data demonstrate that removing BMSCs from their normal environment reduces their osteoblastic capacity and that to achieve their maximal differentiation, BMSCs require direct physical contact with accessory cells such as megakaryocytes. These findings may be of direct relevance to the use of BMSCs for tissue-engineering purposes.

Clinical and pathological criteria for the diagnosis of essential thrombocythemia, polycythemia vera, and idiopathic myelofibrosis (agnogenic myeloid metaplasia)

A set of clinical and pathological criteria for the diagnosis and staging of Philadelphia chromosome-negative myeloproliferative disorders (Ph(1-)-MPDs) is presented by including bone marrow histopathology as a significant tool to identify the early, manifest, and advanced stages of essential thrombocythemia (ET), polycythemia vera (PV), and idiopathic myelofibrosis/agnogenic myeloid metaplasia (IMF/AMM). This combined approach provides a pathognomonic clue to each of the different subtypes of Ph(1-)-MPDs and further enables recognition of the various steps in the evolution of the myeloproliferative process Increase and clustering of giant to large megakaryocytes with mature cytoplasm and multilobulated staghorn-like nuclei in a normal or only slightly increased cellular bone marrow represent major hallmarks of ET. Loose assemblies of small to giant pleiomorphic megakaryocytes containing deeply lobulated nuclei together with a proliferation of erythro- and granulopoiesis (panmyelosis) are the specific lesions of PV. The initial prefibrotic and the overt and more advanced myelofibrotic stages of IMF/AMM show a pronounced proliferation of an abnormal megakaryo- and granulopoiesis dominated by clustered atypical medium-sized to giant megakaryocytes with cloud-like, bulbous, and often hyperchromatic nuclei, which are not seen in allied subtypes of MPDs including chronic myeloid leukemia (Ph(1+)-CML) and myelodysplastic syndromes (MDS). The presented clinical and pathological criteria modify the Polycythemia Vera Study Group (PVSG) proposals for the Ph(1-)-MPDs by including bone marrow histopathology and are in keeping with features outlined in the new World Health Organization classification. The latter allows the differentiation of true ET from reactive thrombocytosis and from thrombocythemias as an eventually presenting finding in PV, IMF/AMM, MDS, and Ph(1+)-CML. Moreover, these diagnostic guidelines are able to separate latent and early PV from secondary erythrocytosis and to detect the prefibrotic and early stages of IMF/AMM. Myelofibrosis is not a feature of ET and is rarely observed in PV at time of diagnosis, but it becomes apparent during long-term follow-up and constitutes a prominent lesion during the course of IMF/ AMM. Life expectancy is almost normal in ET and is also not significantly altered during the first, but compromised during the second, decade of follow-up in PV. On the other hand, survival is substantially shortened in IMF/AMM, even for patients with thrombocythemia as a frequent finding of prefibrotic and early stage IMF/AMM.

Polycythemia rubra vera versus secondary polycythemias. A clinicopathological evaluation of distinctive features in 199 patients

To determine parameters of distinctive value in polycythemia rubra vera (PV) versus secondary polycythemias (SP), a clinicopathological study was performed on 199 patients. These presented with a borderline to marked elevation of the hemoglobin level (> 18 g/dl in men and > 16 g/dl in women). Evaluations of clinical features and bone marrow histopathology were carried out independently. According to the results derived from laboratory data and representative pretreatment trephine biopsies, three groups of patients emerged: group I presenting with the concordant clinical and morphological findings of early to manifest PV (136 patients), group II consisting of 55 patients with the congruent signs and symptoms of SP mostly caused by various chronic bronchopulmonal disorders, and finally eight patients (group III) with divergent findings. Between group I and II patients (PV versus SP), a number of clinical parameters proved to be significantly different. With the exception, of the red cell mass, platelet count, leukocyte alkaline phosphatase, LDH, spleen size, and the erythropoietin level had a significantly discriminating impact. Morphological features of distinctive value consisted of a set of specific lesions. Contrasting SP with an only borderline to slight increase in cellularity associated with a moderate enlargement of the erythroblastic islets, PV was always characterized by a significant increase in hematopoiesis, revealing a trilinear proliferation (panmyelosis). Megakaryopoiesis was strikingly different in PV as compared to SP by displaying clustering and a pleomorphous appearance. i.e., very small and giant megakaryocytes with staghorn-like nuclei were neighboring each other. Moreover, conspicuous alterations of the interstitial compartment were recognizable in SP. These consisted of deposits of cell debris in histiocytic reticular cells, iron-laden macrophages, and a plasmacytosis, implying an inflammatory reaction. These changes were only very rarely observed in PV, as opposed to a minimal to slight increase in reticulin fibers in about 12% of patients. In conclusion, a more elaborate evaluation of bone marrow features resulted in a set of diagnostic criteria with discriminating capacity that should be considered in prospective clinical trials.

Clinicopathology and histochemistry on bone marrow biopsies in chronic myeloproliferative disorders--a clue to diagnosis and classification

A clinicopathological study was carried out to address the currently still controversial issues of: 1) thrombocythaemias in chronic myeloproliferative disorders (MPDs); 2) Initial, prefibrotic idiopathic myelofibrosis (IMF); 3) discrimination of spurious polycythaemic states or polyglobuly (PG) from polycythaemia vera (PV); 4) unclassifiable MPDs. Based on a synoptical approach which implicates a comparative evaluation of laboratory data and histopathology of the bone marrow, the discriminating efficiency of both diagnostic tools has been emphasized. An elaborate evaluation of histotopography and cytological appearance of megakaryopoiesis is an invaluable aid to distinguish the different subtypes of MPDs which may eventually present with a significant elevation of the platelet count. Prefibrotic IMF is not only associated with a certain set of clinical symptoms (minimal to slight anaemia, splenomegaly, thrombocytosis), but should also be characterized by specific alterations of bone marrow morphology. Moreover, follow-up studies are in keeping with the finding that these patients evolve into typical IMF regarding laboratory parameters and ensuing myelofibrosis. Smokers polycythaemia--PG may be separated from early PV by the significant raise in the red cell mass and also by a few, easily determinable clinical parameters (i.e. EPO level, thrombocytosis, LAP). Both conditions can be distinguished by regarding bone marrow features (megakaryopoiesis, interstitial changes) which exert a distinctive impact. According to our experience the majority of patients categorized as unclassifiable MPDs include cases in which clinical or morphological data are inadequate to permit a more precise diagnosis. Only in a small proportion not a failing methodology, but initial stages of the disease process requires sequential examinations to reach a correct diagnosis.

Megakaryopoiesis and myelofibrosis in chronic myeloid leukemia after allogeneic bone marrow transplantation: an immunohistochemical study of 127 patients

An immunohistochemical and morphometric study was performed on 363 trephine biopsies of the bone marrow derived from 127 patients with chronic myeloid leukemia at standardized end points before and after allogeneic bone marrow transplantation (BMT). The purpose of this investigation was to evaluate features of CD61+ megakaryopoiesis related to successful engraftment. Further, we tried to elucidate possible associations of this lineage, including precursor cells, with the platelet count and reticulin fibrosis during the pretransplant and, specifically, post-transplant periods. A significant correlation was recognizable between the quantity of CD61+ megakaryocytes and the platelet values before BMT and also after completed hematopoietic recovery. In the very early post-transplant period, which is associated with severe thrombocytopenia, patchy regeneration of disarranged hematopoiesis occurred, including dysplastic megakaryocytes. According to planimetric measurements after BMT, the atypical micromegakaryocytes characteristic for chronic myeloid leukemia disappeared, and the engrafted donor bone marrow revealed a prevalence of normal-size cells of this lineage. On the other hand, normalization of megakaryocyte size was absent in sequential examinations of the few patients with a leukemic relapse who had a predominance of atypical dwarf forms comparable with chronic myeloid leukemia. Before BMT occurred, reticulin fiber density was significantly correlated with the number of CD61+ megakaryocytes and its precursor cell population. In 34 patients with myelofibrosis that occurred after myelo-ablative therapy and BMT, an initial regression was followed by an insidious recurrence of fibers concentrated in the areas of regenerating hematopoiesis. This postgraft reappearance of reticulin fibrosis was significantly associated with the quantity of megakaryocytes. Regarding engraftment parameters, pretransplant presence of (reticulin) myelofibrosis exerted a distinctive impact because of a delayed hematopoietic reconstitution according to standard clinical criteria. In line with this finding, slowed engraftment was also significantly related with higher pretransplant megakaryocyte and platelet counts.

Selectins (CD62L, CD62P) and megakaryocytic glycoproteins (CD41a, CD42b) mediate megakaryocyte-fibroblast interactions in human bone marrow

Previous in vitro studies are in keeping with the finding that isolated and enriched megakaryocytes attach to bone marrow fibroblasts and generate an increased growth of these cells. This process was assumed to depend on a close spatial relationship between both cell types which supports the paracrine effect of platelet-derived growth factor (PDGF) and transforming growth factor (TGF)-beta1. Moreover, adhesion molecules including beta1 integrin receptors and fucosylated structures were determined to play an important role in these complex interactions. However, up to now the influence of megakaryocyte expressed glycoproteins CD41a and CD42b in these processes was not investigated. In addition, the role of megakaryocytic CD62P and also of CD62L, both adhesion molecules of the selectin group, could also be of interest. Following isolation and enrichment of bone marrow megakaryocytes and fibroblasts, both cell populations were characterized regarding their expression of these factors by applying immunocytochemical techniques. Additionally, their influence on adhesion of megakaryocytes to fibroblasts as well as fibroblast growth was evaluated by comparative megakaryocyte-fibroblast co-cultures and inhibition studies using specific monoclonal antibodies (mabs). Fibroblast monocultures served as controls. In these experiments, selectin-specific antibodies significantly reduced megakaryocyte attachment to fibroblast feeder layers and fibroblast growth in the co-cultures. The effect of CD41a and CD42b specific antibodies was limited to megakaryocyte-dependent fibroblast growth. These results elucidate the involvement of the selectins CD62P and CD62L in the basal activation of megakaryocytes inducing their attachment to bone marrow fibroblasts. In contrast, the megakaryocyte glycoproteins CD41a and CD42b exert their effect on the megakaryocyte dependent fibroblast growth. Altogether, it is tempting to speculate that the various interactions of these mediators reflect certain steps in the complex pathomechanisms causing the evolution of (reactive) myelofibrosis in hematopoietic neoplasias accompanied by megakaryocytic proliferation.

Changing patterns of histological subgroups during therapy of Ph1+ chronic myelogenous leukaemia

AIMS

Bone marrow histopathology reveals a striking heterogeneity at diagnosis of Philadelphia chromosome positive (Ph1+) chronic myelogenous leukaemia (CML). Based on semiquantitative evaluations of the number of megakaryocytes and the content of fibres, various histological subtypes have been postulated. However, little information exists on whether these groups represent stable categories of the different classification systems and whether therapeutic regimes exert any influence on the putative shift of histological patterns.

METHODS AND RESULTS

A retrospective clinicopathological study was performed on 396 bone marrow biopsies derived from 173 patients. There were at least two representative trephines taken at diagnosis and at median intervals of 16 months. Processing of the specimens involved immunostaining with CD61 (megakaryopoiesis) and Ret40f (erythropoiesis) and Gomori's silver impregnation technique. Based on morphometric analysis and in accordance with the general appearance of bone marrow histology three different histological subtypes were distinguished. These consisted of a granulocytic (51 patients), a predominantly megakaryocytic (73 patients) and a myelofibrotic pattern (49 patients). Follow-up biopsies revealed that a significant transition of histological groups occurred and that, independently of treatment modalities, the myelofibrotic category was associated with an unfavourable prognosis. Of the 124 patients without myelofibrosis at onset, 42% later transformed into the myelofibrotic subtype. However, these patients showed no prevalence of either a pre-existing granulocytic or megakaryocytic growth. Myelofibrotic changes were significantly associated with interferon (IFN) and busulfan (BU) therapy. On the other hand, a transition of a myelofibrotic into a nonfibrotic subtype was detectable in 17 of the 49 patients under study and related to hydroxyurea (HU) treatment.

CONCLUSIONS

Histological classification systems of bone marrow features in CML do not represent stable patterns, but may be significantly altered by therapy, in particular IFN and HU.

Fibre content and cellularity of the bone marrow of the iliac crest, vertebral column and sternum in chronic myeloproliferative disorders

Heterogeneous content of fibres and haematopoesis within the bone marrow may affect diagnosis and staging in chronic myeloproliferative disorders (CMPDs). To evaluate their distribution, we conducted a post mortem histomorphometric study of 22 patients with CMPD in chronic phases. In bone marrow specimens from the anterior and posterior iliac crest (right and left of each), the sternum, the 7th thoracic and the 3rd lumbar vertebra, the argyrophil fibres were counted using the line intersection method and the cellular and fatty bone marrow using the point count method. Statistical analysis was performed by direct comparison of the sites. The distribution of fibres was almost homogeneous in the patients with low fibre content, revealing a random diversity in more advanced stages of marrow fibrosis. 1/22 patient had no fibre increase in one specimen of the iliac crest and overt myelofibrosis in the other sites. 1/22 patient had myelofibrosis in two sites of the iliac crest and no fibre increase in vertebral column and sternum. The bone marrow cellularity was almost homogeneously increased in all patients. Myelofibrosis proved to be a generalised process with heterogeneous grades of severity in different regions of the bone marrow in CMPDs. No topographical bias was found. In contrast to the homogeneous increase of the bone marrow cellularity the topographical heterogeneity of the fibre content may limit the representativity of single bone marrow biopsies in patients with CMPDs.

Bone marrow features and clinical findings in chronic myeloid leukemia--a comparative, multicenter, immunohistological and morphometric study on 614 patients

A multicenter, immunohistochemical and morphometric study was performed on diagnostic pretreatment bone marrow biopsies in 614 adult patients with Ph1+ chronic myeloid leukemia (CML) to compare histological features with clinical findings. For identification of megakaryopoiesis we used the monoclonal antibody CD61 and additionally the PAS reaction to determine the subfraction of atypical micromegakaryocytes and precursors. Labelling of erythroid precursors was carried out by a monoclonal antibody directed against glycophorin C. In order to selectively stain macrophages and their activated subset we applied CD68 and the GSA-I lectin. Density of argyrophilic fibers (reticulin plus collagen) was measured following Gomori's silver impregnation method. In accordance with laboratory data morphological variables revealed a comparable amount of congruence in the various groups of CML patients derived from different sources. In about 26% of patients early (reticulin) to advanced (collagen) fibrosis was detectable. Significant correlations were calculated between the extent of myelofibrosis with splenomegaly, anemia and increasing numbers of erythroblasts and myeloblasts in the peripheral blood count. These features were assumed to indicate more advanced stages of the disease process with ensuing transition into myeloid metaplasia and consequently were associated with an unfavorable prognosis. Significant relationships were revealed between the number of CD61+ megakaryocytes and more important, also their precursor fraction with the degree of fibrosis. This result extends previous experimental findings regarding the impact of immature elements of this cell lineage for the generation of myelofibrosis. The significant association of erythroid precursors with the number of mature (resident) macrophages including their activated GSA-I subset may shed some light on their functional involvement in iron turnover and hemoglobin synthesis. A modified histological classification of predominant bone marrow features is introduced. This simplified synthesis staging system (Cologne Classification) is not only associated with certain sets of laboratory data, but also with different survival patterns.

Myelodysplastic syndrome (MDS), acute myeloid leukaemia (AML) and chronic myeloproliferative disorder (CMPD) in cats

Histological, enzyme histochemical and ultrastructural findings in three cases of feline bone marrow neoplasia are described. The following changes were observed: in myelodysplastic syndrome (MDS), a low medullary blast count, strongly atypical (micromegakaryocytic) proliferative megakaryocytopoiesis, hypoplastic erythrocytopoiesis with impairment of differentiation, multifocal extravasation and lymphoid aggregates; in acute myeloid leukaemia (AML), medullary proliferation of undifferentiated cell types; in chronic myeloIproliferative disorder (CMPD), trilinear medullary proliferation with complete cellular maturation, osteomyelosclerosis and extramedullary haemopoiesis. In two cases (MDS, AML), ultrastructural demonstration of C-type virus particles (feline leukaemia virus) suggested a viral aetiology.

Clinicopathological diagnosis and differential criteria of thrombocythemias in various myeloproliferative disorders by histopathology, histochemistry and immunostaining from bone marrow biopsies

Differentiation of essential thrombocythemia (ET) from thrombocythemias occurring in various subtypes of chronic myeloproliferative disorders (MPDs) is controversial, because of the lack of uniform clinical and morphological criteria. A retrospective clinicopathologic study was performed on 375 patients presenting with a MPD and a platelet count exceeding 500 x 10(9/)l. For comparison 35 patients with reactive thrombocytosis (RT) and five patients with a myelodysplastic syndrome (MDS-5q(-) syndrome) were enrolled into this study. In addition to a complete clinicopathological work-up, procedures included histochemical and immunological staining techniques and morphometry of bone marrow biopsies for proper evaluation of megakaryocytes (CD61) and erythroid precursors (Ret40f). Because of the high patient's age on admission, relative survival rates with corresponding disease-specific loss of life expectancy were calculated. Analysis of clinical and morphological characteristics, in particular megakaryopoiesis revealed features which enabled a clear-cut distinction between thrombocythemias in MPDs and thrombocythemic states in MDS. This rationale proved to be most important for the diagnostic discrimination of the 33 patients with initial (prefibrotic) stages of idiopathic myelofibrosis (IMF) from ET (40 patients). A new set of relevant criteria for the diagnosis of IMF with special regard to early stages and its distinction from ET has been proposed. Hemorrhagic episodes were more frequently observed in ET than in thrombocythemias associated with polycythemia vera (PV). Computation of specific loss of life expectancy revealed two extremes: thrombocythemia in CML (81%) and ET (3%), whereas thrombocythemias in PV and IMF did not show a significantly different life loss (19-22%). The revised criteria for ET, PV and IMF are reliable by taking histopathological features from bone marrow biopsies into consideration, particularly for the diagnosis of ET and its differentiation from thrombocythemias as a presenting symptom accompanying the various subtypes of MPDs.

Evidence for integrin receptor involvement in megakaryocyte-fibroblast interaction: a possible pathomechanism for the evolution of myelofibrosis

Megakaryocytes are assumed to be functionally linked with the evolution of myelofibrosis, complicating chronic myeloproliferative disorders. It has already been shown that megakaryocytes will promote fibroblast growth in vitro when in spatial proximity. Here, we demonstrate that the integrin receptors alpha3beta1 and alpha5beta1 are involved in this megakaryocyte-fibroblast interaction. Upon addition of anti-alpha3 and -alpha5 antibodies to megakaryocyte-fibroblast cocultures, fibroblast growth was significantly impaired, and megakaryocyte attachment to the fibroblast feederlayer was significantly reduced. Unilateral blocking of megakaryocytes with anti-alpha3 or -alpha5 antibodies resulted in a suppression of adhesion, probably reflecting the prominent function of fibronectin receptors on the megakaryocyte surface. Moreover, the oligopeptide RGDS (Asp-Gly-Asp-Ser) caused a significant reduction of fibroblast growth as well as megakaryocyte adhesion. This feature reinforces that fibronectin receptors are involved. In addition, fibroblast proliferation was impaired by the application of fibronectin antibodies recognizing the cell-binding domain. However, no effect was observable with respect to megakaryocyte adhesion. In conclusion, our in vitro studies demonstrate the involvement of beta1-integrins, in particular the fibronectin receptor in the megakaryocyte-dependent fibroblast proliferation and therefore suggest a pivotal role of megakaryocytes in the complex pathomechanism causing myelofibrosis.

Should a platelet limit of 600 x 10(9)/l be used as a diagnostic criterion in essential thrombocythaemia? An analysis of the natural course including early stages

In order to evaluate the natural history of essential thrombocythaemia (ET), clinical data and prognostic factors of 143 patients with ET were retrospectively analysed (mean observation time 6.1 +/- 4.6 years). In 42 patients the early phase of the disease with initial platelet counts between 250 and 600 x 10(9)/l was assessed. In most early cases, ET was suggested by clinical symptoms (79%) and increased megakaryopoiesis (95%) with abnormal megakaryocytes in bone marrow histology (n = 34) and cytology (n = 5). Other myeloproliferative disorders and reactive thrombocytosis were excluded according to the diagnostic criteria of the Polycythemia Vera Study Group. During follow-up of the 38 early cases not treated cytoreductively at diagnosis, the platelet counts increased to >600 x 10(9)/l in 28 patients (74%) and remained between 450 and 600 x 10(9)/l in 10 patients (26%). In primarily asymptomatic patients (n = 46) with initial platelet counts above (n = 37) and below 600 x 10(9)/l (n = 9) the rates of increase of symptomatic patients were similar at about 7% per year. No influence of the initial platelet count on survival was seen in multivariate analysis of prognostic factors which included all 143 cases. Survival was mainly influenced by the rate of ET-related complications during follow-up (P = 0.002). Analysing the influence of cytoreductive therapy on symptom-free survival, platelet reduction benefited patients under 60 years (19 cytoreductively treated v 65 untreated patients, P = 0.075). The results demonstrate the possible clinical relevance of the early stages of ET and suggest that the features of pathologic megakaryopoiesis in the bone marrow are a more reliable diagnostic criterion than a definite platelet limit. Therefore, further therapeutic studies should include all stages of the disease and all age groups.

Prognostic factors in idiopathic (primary) osteomyelofibrosis

BACKGROUND

Prognostic variables for idiopathic (primary) osteomyelofibrosis (IMF) are ill-defined because of the lack of large control studies based on uniform diagnostic criteria.

METHODS

A retrospective clinicopathologic study was performed on 250 consecutively recruited patients (115 males and 135 females) with an established diagnosis of IMF. In contrast to previous studies, the current study cohort encompassed the full spectrum of initial to advanced stages of the disease process according to laboratory data and particularly histology. Because of the relatively high patient age on admission (median, 66.5 years), relative survival rates with corresponding life expectancies and disease specific life loss were calculated. Moreover, a classification and regression tree (CART) analysis was performed to segregate the study patients into subgroups with significantly different prognosis.

RESULTS

Analysis of the life expectancy and the proportion of deaths attributable to IMF showed a global reduction in life expectancy of 31%. Further calculation disclosed a consistently greater impact of disease in older patients. Age, hemoglobin level on admission, and leukocyte and thrombocyte counts remained as the most relevant parameters for prognosis in multivariate consideration (CART analysis) and facilitated a clear-cut separation into three risk groups. The life expectancy of low risk patients was approximately 10 times higher than that of high risk patients (22.07 years vs. 2.25 years).

CONCLUSIONS

These results are in keeping with the assumption that features signaling bone marrow insufficiency are associated with a worsening of survival. Generalization, indicated by myeloid metaplasia, can occur at every stage, even in so-called hypercellular phases of IMF. Conversely, myelofibrosis alone is not necessarily predictive of poor survival.

Clinicopathological impact of the interaction between megakaryocytes and myeloid stroma in chronic myeloproliferative disorders: a concise update

In this report an attempt has been made to discuss some of the issues pertinent to myelofibrosis complicating chronic myeloproliferative disorders (CMPDs) that are significantly associated with megakaryocyte function. In this context, biochemical, clinical and particularly morphological features were reviewed. Morphological findings based on elaborate techniques were in keeping with the assumption that in chronic myeloid leukemia (1) the number of CD61-positive megakaryocytes, and in particular their precursors were the parameters most closely associated with myelofibrosis (2) an increased content of reticulin fibers in follow-up biopsies significantly correlated with laboratory data indicative of a high tumor burden (anemia, peripheral blasts, hepatosplenomegaly) and thus a more advanced stage of the disease process (3) even a slight increase in reticulin, i.e. doubling of the normal fiber density was associated with a worse prognosis independent of therapeutic regimens given (4) Dynamics of myelofibrosis was significantly influenced by treatment. In this context, calculation of the myelofibrosis progression index (MPI) revealed a higher score following interferon therapy compared with busulfan. In addition, in idiopathic myelofibrosis (5) the evolution of myelofibrosis was unpredictable and according to the MPI, progression occurred at a relatively low rate (6) proliferation and dilatation of sinusoids accompanying intravascular hematopoiesis and collagen type IV deposits were predominant features in later (fibro-osteosclerotic) stages in the course of disease (7) transmural migration of megakaryocytes demonstrated by three dimensional reconstruction revealed a mole-like tunneling through the thickened sinusoidal wall. A very careful assessment of the numerous correlations between bone marrow features and laboratory data will allow clinicians and pathologists to gain a better insight into the mutual relationships between hematological and morphological findings in CMPDs.

The myeloproliferative disorders. An historical appraisal and personal experiences

According to strict morphological, biochemical and cytogenetic criteria Philadelphia chromosome positive essential thrombocythemia and chronic granulocytic leukemia constitute a separate malignant and individual disease entity, whereas Philadelphia chromosome negative essential thrombocythemia, polycythemia vera and agnogenic or megakaryocytic myeloid metaplasia form a chronic proliferation of three hematopoietic cell lines. Histopathology from bone marrow biopsies permits the characterization and diagnostic differention of the various myeloproliferative disorders and appears to be a main and specific diagostic criterion for polycythemia vera and essential thrombocythemia. Hemorrhagic thrombocythemia is a clinical syndrome of recurrent spontaneous mucocutaneous and secondary hemorrhages often preceded by thromboses, extremely high platelet counts, pseudohyperkalemia, increased bone marrow cellularity and frequently splenomegaly. The diagnostic criteria of essential thrombocythemia with paradoxical occurrence of thrombotic events and hemorrhagic manifestations are a platelet count in excess of 1000 x 10(9)/L and increased bone marrow cellularity in the majority of the cases. Erythromelalgia and other microcirculatory ischemic or thrombotic events or accidents in essential thrombocythemia and polycythemia vera already occur at platelet counts in excess of the upper limit of normal. First line treatment options in essential thrombocythemia and polycythemia vera are control of platelet function with low-dose aspirin and reductive control of platelet count and erythrocytes by bloodletting, interferon and busulfan or hydroxyurea monochemotherapy.

Idiopathic primary osteo-myelofibrosis: a clinico-pathological study on 208 patients with special emphasis on evolution of disease features, differentiation from essential thrombocythemia and variables of prognostic impact

A retrospective clinico-pathological study was performed on 208 consecutively recruited patients (94 males, 114 females, median age 67 years) with idiopathic (primary) osteo-/ myelofibrosis (IMF). According to bone marrow histology (cellularity) as well as extent (semiquantitative grading) and quality (reticulin/collagen) of myelofibrosis, stages of the disease process were determined. At closure of this study (observation time 65 months) 133 patients were dead and 75 alive and median survival was 56 months. The wide spectrum of clinical signs and symptoms and laboratory data on admission was reflected by a corresponding variety of histological features. Significant differences of hematological values could be calculated between patients with or without early reticulin fibrosis (fiber scores 0 and 1) and advanced fibro-osteosclerotic stages (fiber scores 2 and 3). Evolution of disease features was elicited by longitudinal follow-up studies and sequential bone marrow biopsies. Morphometric assessment of fiber density in patients without preceding chemotherapy revealed an unpredictable and varying progression of myelofibrosis associated with alterations of certain laboratory parameters (hemoglobin level, spleensize, thrombocytosis). Differentiation from essential (primary) thrombocythemia (ET) was required in 25 patients who fulfilled the postulated diagnostic criteria. In fact, this group was consistent with hypercellular, early stages of IMF without relevant reticulin fibrosis and an excessively raised platelet count (> or = 1000 x 10(9)/1). Discrimination was only feasible by regarding histology carefully, particularly abnormalities of megakaryopoiesis and follow-up data. Parameters of predictive value indicating a significant loss in life expectancy in comparison with a sex- and age-adjusted normal population included: age (> or = 60 years), hemoglobin levels (< or = 10 g/dl), thrombocyte count (< or = 600 x 10(9)/1) and the presence of myeloblasts and promyelocytes. Statistical analysis disclosed that in the so-called early stages of IMF without relevant myelofibrosis, findings indicative for extramedullary hemopoiesis or generalization of the disease process exerted an unfavourable influence on survival.

Effect of interferon therapy on bone marrow morphology in chronic myeloid leukemia: a cytochemical and immunohistochemical study of trephine biopsies

The effect of interferon (IFN) therapy on bone marrow features in chronic myeloid leukemia (CML) has been studied on successive trephine biopsies (mean interval 13 +/- 8 months) by cytochemical and immunohistochemical methods in combination with morphometry and in comparison with a control group of patients who received monotherapy by busulfan (BU). Following IFN administration (IFN-alpha frequently in combination with IFN-gamma), there was a decrease in neutrophil granulopoiesis accompanied by a significant expansion of erythroid precursors and increased numbers of hemosiderin-laden macrophages. These changes corresponded with the hematologic response in 21 of the 25 patients investigated. Numbers of megakaryocytes and reticulin/collagen fiber density increased during treatment. Most conspicuously, in responding patients atypical micromegakaryocytes, usually characterizing CML, were partially replaced by normal-sized cells of this lineage. These features are in keeping with the assumption of a reappearance of the normal hematopoietic cell clone as the result of IFN therapy, which was not found in the BU-treated control group. On the other hand, a relevant subpopulation of micromegakaryocytes (about 30%) was still maintained. This result probably relates to the failure to improve myelofibrosis more effectively. Analysis of cell proliferation (proliferating cell nuclear antigen-PCNA) and apoptosis (in situ end labeling) revealed a reduction in PCNA labeling and increased numbers of cells undergoing programmed death. Identification of the activated subset of macrophages (alpha-D-galactosyl residues expression) by appropriate lectin histochemistry disclosed an increase in the number of GSA-I binding cells. These findings were exclusively limited to IFN administration and reflect an inhibitory effect of IFN on cell proliferation and stimulation of programmed cell death. The latter phenomenon probably results in increased phagocytosis of clonally transformed myeloid cells by GSA-I-positive (activated) macrophages.

Megakaryocytes and fibroblasts--interactions as determined in normal human bone marrow specimens

An in vitro study was performed to investigate possible interactions between megakaryocytes and bone marrow fibroblasts, both obtained from healthy donors. We were able to demonstrate that the proliferation of fibroblasts increased significantly by co-culturing these cells with megakaryocytes for 6 days. Addition of neutralizing antibodies for PDGF and TGF beta 1, caused a significant reduction of fibroblast growth. Inhibition of cell to cell contacts via tissue culture inserts generated a conspicuous impairment of fibroblast proliferation compared with megakaryocyte-fibroblast co-cultures, where contact was allowed. Hence, our findings suggest that a close spatial relationship between megakaryocytes and fibroblasts is needed for the activation of growth in normal human bone marrow. Neighbouring of megakaryocytes and fibroblasts seems to be necessary in order to achieve a certain threshold of local growth factor concentration. Our results are in keeping with the assumption that PDGF and TGF beta 1, are secreted by normal human megakaryocytes in very low concentrations and promote significantly fibroblast proliferation.

Influence of cytokines (IL-1 alpha, IL-3, IL-11, GM-CSF) on megakaryocyte-fibroblast interactions in normal human bone marrow

The evolution of myelofibrosis accompanying chronic myeloproliferative disorders (CMPDs) is often linked with megakaryopoiesis. However, it is not known whether or to what extent megakaryocytes of normal human bone marrow are capable of stimulating fibroblast growth. For this reason, an in vitro study was performed to elucidate possible cytokine-dependent interactions between megakaryocytes and fibroblasts derived from healthy volunteers. Fibroblast growth was significantly promoted by the presence of megakaryocytes and modulated by additional application of various cytokines. While recombinant human (rh) interleukin (IL)-1 alpha had no obvious effect on fibroblast proliferation, a slight increase was detected on adding granulocyte-macrophage colony stimulating factor (rhGM-CSF). Application of rhIL-3 caused a significant increase in the number of fibroblasts. In contrast, administration of rhIL-11 suppressed the megakaryocyte-dependent growth-promoting effect and co-stimulation with rhIL-3 led to a significant decrease of fibroblast number in comparison to rhIL-3-stimulated co-cultures. Inhibition of cell-cell contact in unstimulated, as well as in rhIL-3-stimulated co-cultured led to a conspicuous impairment of fibroblast growth. A similar effect was observed when neutralizing antibodies directed against platelet-derived growth factor (PDGF) and transforming growth factor (TGF)beta 1 were added to rhIL-3-stimulated cultures. Our findings are in keeping with the assumption that interactions between megakaryocytes and fibroblasts involve in cytokine-mediated functional network regulated by factors such as spatial relationship, cytokine stimulation, and low concentrations of mediators, particularly PDGF and TGF beta. In this complex system rhIL-3 seems to play a crucial role in the promotion of these various interrelationships.

Pulmonary fibrosis with megakaryocytoid cell infiltration and chronic myelogenous leukemia

The relationship between fibrosis and megakaryocytic infiltration in the lungs of patients with Philadelphia-chromosome (Ph1)-positive chronic myelogenous leukemia (CML) is the focus of this review. Ph1-positive megakaryocytes are thought to reach and accumulate in the pulmonary vasculature through the marrow-blood barrier. In 21 autopsied patients with accelerated phase or blastic crisis of CML, megakaryocytic infiltration to the lungs was demonstrated in 10 patients, myelofibrosis in 12 patients and both in 5 patients. In 2 of the 10 patients with increased megakaryocytes in the lungs, relatively new fibrosis and alveolar damage in the acute phase were demonstrated with the simultaneous occurrence of myelofibrosis-"myelopulmonary fibrosis."Leakage of mitogenic factors resulting from an abnormality in the packaging mechanism of alpha-granules in these cells termed acquired grey platelet syndrome could cause fibrosis in the lungs as well as the bone marrow.

Evolution of fibro-osteosclerotic bone marrow lesions in primary (idiopathic) osteomyelofibrosis--a histomorphometric study on sequential trephine biopsies

Evolution of fibro-osteosclerotic bone marrow lesions in the course of primary (idiopathic) osteomyelofibrosis (OMF) was studied in 36 patients (17 males, 19 females; median age 57 years) by morphometric evaluation of sequential trephine biopsies. The mean interval between first and terminal examination was 33 months (range 6 to 121 months). Two biopsies were performed in 31 and three and more in five patients. Morphometry consisted of a determination of argyrophilic (reticulin and collagen) fiber density, measured per area of hematopoiesis or marrow cellularity, and the calculation of the extent of trabecular bone tissue. In 13 of our 36 patients increase in reticulin and collagen deposits was only borderline to minimal during the observation period. On the other hand, in 23 of the 36 patients a slight to gross accumulation of reticulin and collagen fibers, partially associated with osteosclerotic changes was recognizable. No regression of fibrosis was encountered in our cohort of patients which included three cases with preceding low-dose busulfan therapy. Analysis of the different lengths of intervals between the first and the last biopsy and degree of fibrosis as well as osteosclerosis, suggested that alterations developed progressively, however, at an unpredictable and considerably varying rate. Thus our findings were not in keeping with several studies on smaller series of patients, which generally contested a progression of fibro-osteosclerotic lesions in OMF and additionally reported reversal of the pathology following chemotherapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Erythropoiesis in primary (idiopathic) osteomyelofibrosis: quantification, PCNA-reactivity, and prognostic impact

In 64 patients with primary (idiopathic) osteomyelofibrosis (OMF), a morphometric analysis has been performed on bone marrow trephine biopsies following sequential double-immunostaining with monoclonal antibodies against proliferating cell nuclear antigen (PCNA) and erythroid precursor cells (glycophorin C). The purpose of this study was to quantify erythropoiesis and its PCNA-staining capacity and, further, to determine the impact of these parameters for the development of anemia and for prognosis. In comparison with a control group (15 patients), a significant reduction in the number of erythro-normoblasts could be demonstrated, associated with an increase in PCNA-labelling. Moreover, significant correlations between the amount of nucleated erythroid marrow cells and degree of anemia (hemoglobin level, hematocrit, erythrocyte count) and survival could be calculated. Adverse relationships were assessed between number of erythroid cells, thrombocyte count, and spleen size, and also argyrophilic (reticulin/collagen) fiber density. These interactions were thought to reflect the biological behaviour of the disease process, i.e., the progression or extent of myeloid metaplasia. Our findings support ferrokinetic studies suggesting erythroid hypoplasia as one of the major causes of anemia in OMF. The remarkable high PCNA-labelling index of the macrocytic-megaloblastoid appearing erythropoiesis is probably caused by an overexpression of this marker protein. A comparative evaluation of Ki-67 antigen immunostaining in splenic tissue (myeloid metaplasia) and of the PCNA-labelling in pernicious anemia lend support to the assumption of an undue prolongation of the S-phase generated by secondary folate (hematinic) deficiency.

Primary myelofibrosis: a detailed statistical analysis of the clinicopathological variables influencing survival

In the present study we analyzed the prognostic significance of several clinical, hematological, and histological parameters recorded at diagnosis in a consecutive series of 72 patients with primary myelofibrosis (PMF). Univariate analysis showed that the most significant indicators of poor survival were the following: age greater than 60, splenomegaly, anemia (hemoglobin > 10 g/dl), leukopenia (WBC < 4 x 10(9)/l or leukocytosis > 14 x 10(9)/l), and any of these histological features: adipose tissue and megakaryocyte reduction, prominent osteoblastic rims along the trabecular bone, presence of peritrabecular megakaryocytes (Mk), absence of normal or giant Mk. The multivariate analysis showed that only the level of hemoglobin and the presence of both normal Mk and fever independently influenced the prognosis. These parameters were used to set up a prognostic scoring system, allowing a feasible prognosis to be made for each patient at the time of diagnosis and identifying those patients in urgent need of new therapeutic approaches.

Myelofibrosis in chronic myeloproliferative disorders. Incidence among subtypes according to the Hannover Classification

The distribution and the development of fibrosis were evaluated from bone marrow biopsies of patients with chronic myeloproliferative disorders (CMPD), regarding two groups of patients: (1) 564 with follow-up biopsies over a period of up to twelve years observation time, and (2) 1.787 diagnostic bone marrow biopsies from CMPD patients. Fibrosis was divided into three grades of fiber increase: early myelosclerosis, myelofibrosis, and advanced myelofibrosis. The first group of sequential BMB showed a significant progress to myelofibrosis in so-called "Chronic Megakaryocytic-Granulocytic Myelosis"--CMGM-, which corresponds to Agnogenic Myeloid Metaplasia-AMM-in 72.4% (21/29 patients), as well as in CML with megakaryocytic increase-CML.MI-in 39.2% (20/51). In the second group of diagnostic biopsies, only 30% of CMGM cases showed no fibrosis. In P. vera, 16.2% (18/111) developed myelofibrosis up to twelve years later. This figure was 4.3% (2/46) in Primary Thrombocythemia. Increase of megakaryocytes in CML indicates a high risk for developing fibrosis, combined with reduced life expectancy.

Morphometric study of the bone marrow in polycythemia vera following interferon-alpha therapy

Bone marrow cellularity and extent of fibrotic change were determined in nineteen patients with polycythemia vera, treated with interferon-alpha (IFN) for 1 year. The cellularity was evaluated with an interactive semiautomatic method using Leitz TAS plus microscope: in particular, number and size of megakaryocytes were evaluated after immunostaining with Y2/51 (CD 61); reticulin content was studied by light microscope with a semiquantitative method. Before IFN therapy mean cellularity was 80.5% (+/- 13.7). After 6 and 12 months mean cellularity was 75.4% and 68.4% respectively. Six months after cessation of IFN therapy the cellularity was 69.1%. A decrease of the number, density and morphometrical parameters of megakaryocytes was also remarked. Reticulin fibrosis was mild in 13 cases and moderate in 6 cases before IFN therapy. Reticulin content was unmodified during therapy in all cases but two, in which fibrosis changed from mild to moderate. In conclusion IFN therapy is to be considered a good method in polycythemia vera for the control of proliferative activity of bone marrow but with IFN therapy one cannot determine regression of marrow fibrosis.

Potential of bone marrow biopsy in chronic myeloproliferative disorders (MPD)

The chronic myeloproliferative disorders (MPD) comprise polycythemia vera (PV), idiopathic thrombocythemia (IT), chronic myeloid leukemia (CML) and myelofibrosis/osteomyelosclerosis (MF/OMS). Bone marrow biopsies of 3500 patients with known or suspected MPD were studied, and the clinical and morphologic variables registered were utilized for multivariate data analysis by selected BMD computer programs. The histologic criteria and the histologic subdivisions, as well as the evolution and prognosis of disease are outlined for each of the clinical entities. The results show that a bone marrow biopsy provides independent diagnostic and prognostic data in this group of hematologic malignancies and therefore constitutes an additional parameter in the diagnostic investigation of patients with suspected or established MPD.

Atypical micromegakaryocytes, promegakaryoblasts and megakaryoblasts: a critical evaluation by immunohistochemistry, cytochemistry and morphometry of bone marrow trephines in chronic myeloid leukemia and myelodysplastic syndromes

A morphometric analysis of bone marrow trephine biopsies has been performed to study the frequency and planimetric characteristics of so-called atypical micromegakaryocytes in chronic myeloid leukemia (CML) and myelodysplastic syndromes (MDS). In addition, an attempt was made to discriminate this particular cell population from small immature elements of megakaryocytopoiesis, such as promegakaryoblasts and megakaryoblasts. The staining reactions employed included periodic acid-Schiff (PAS), alpha-naphthyl acetate esterase (ANAE) and immunohistochemistry with a monoclonal antibody against platelet glycoprotein IIIa (Y2/51-CD61). Comparison of the various staining reactions applied to the different megakaryocytic elements together with morphometric measurements resulted in a clearcut identification of promegakaryoblasts. These were defined as the earliest immature and exclusively CD61-positive precursors. Atypical micromegakaryocytes were characterized by their dysplastic features and strong ANAE reactivity in addition to their positive CD61 staining. When stringent diagnostic criteria (diameter ranging between 10 to 15 microns, mean size about 12 microns) were applied, this abnormal cell population comprised less than 10% of total megakaryocytopoiesis in CML and MDS. It may be assumed that dysmegakaryocytic features in the latter disorders are partially generated by small to medium-sized megakaryocytes (diameter less than 30 microns). In conclusion, the relative frequency of promegakaryoblasts in the normal bone marrow (range 6-8%) is confirmed by evaluation of the immunohistochemical and cytochemical staining methods (CD61 and ANAE). Furthermore, the ANAE reaction facilitates the recognition of atypical micromegakaryocytes as well as small megakaryocytes. Thus cytochemistry provides a better insight into alterations of these cell lineages in various pathological conditions.

The impact of megakaryocyte proliferation of the evolution of myelofibrosis. Histological follow-up study in 186 patients with chronic myeloid leukaemia

A histological study on sequential bone marrow biopsies in patients with chronic myeloid leukaemia (CML) was performed. We wished to answer the question as to whether a different content of megakaryopoiesis in the bone marrow of CML patients has a prognostic significance for the development of myelofibrosis during the course of disease. In addition, the significance of possible changes in the quantity of megakaryopoiesis in this process was assessed. In 186 patients who had no fibre increase at first diagnosis, the rate of subsequent myelofibrosis varied from 19% for the common or granulocytic subtype (CML.CT) to 40% for patients with features of megakaryocytic increase (CML.MI). No significant differences were found either in the rapidity of progression to fibrosis or in the final rate of osteomyelosclerosis. Whereas in CML.MI most patients (75%) showed an increase of fibres only, this was accompanied by an additional increase of megakaryocytes in CML.CT, changing the histological pattern from CML.CT to .MI or .MP, respectively. The data therefore revealed a correlation between fibre increase and subtyping of CML as suggested by the Hannover classification of chronic myeloproliferative diseases. Subtypes of CML with megakaryocytic increase could be shown to present a "pre-myelofibrotic" stage of disease and may therefore be conceived as a particular pathway of acceleration.

Nucleolar organizer regions of megakaryocytes in chronic myeloproliferative disorders

To study megakaryocyte activation, the argyrophilic staining method of nucleolar organizer regions (AgNOR) has been applied to decalcified bone marrow biopsies of 16 individuals with no haematopoietic disorders and 59 patients with chronic myeloproliferative disease. Of the 59 patients, 18 had chronic myeloid leukaemia (CML), 21 chronic megakaryocytic granulocytic myelosis (CMGM), 13 polycythaemia vera (PV) and 7 essential thrombocythaemia (ET). The AgNOR number of megakaryocytes in CML was significantly lower, and in CMGM, PV and ET significantly higher than in healthy individuals. The high number and the clusters of fine-grained AgNORs of megakaryocytes in CMGM, PV and ET are suggestive of active, proliferating cells. The AgNOR number of megakaryocytes and the platelet counts of the patients did not show a convincing correlation. In CMGM, PV and ET the pyknotic, heterochromatinized megakaryocytes with narrow rims of cytoplasm called bare (nude) nuclei, possessed few, large AgNOR granules. The AgNOR staining of bare nuclei and the roughly identical number of granules found in CMGM, PV and ET indicate a common, active mechanism of apoptosis.

Case report: mammographic and sonographic demonstration of extramedullary haematopoiesis of the breast

A female patient with agnogenic myeloid metaplasia presented with hepatosplenomegaly and a palpable mass in the right breast. Mammography showed an asymmetric pattern of confluent densities and sonography revealed several smooth, homogeneous and echo-poor masses of variable sizes in both breasts. Excision biopsy of the mass in the right breast revealed extramedullary haematopoiesis as did histopathologic examination of the liver and the spleen. The data are discussed with emphasis on the complementary character of both diagnostic modalities and the resemblance to lymphoma of the breast, although the findings are too non-specific to rule out breast carcinoma. Knowledge of the clinical history and histopathology are necessary to make the proper diagnosis.

Immunohistochemical evaluation of bone marrow lymphoid nodules in chronic myeloproliferative disorders

One hundred and seventy bone marrow biopsies from patients with chronic myeloproliferative disorders (CMPDs) were evaluated for the presence of lymphoid nodules (LNs) and were immunostained using a panel of monoclonal antibodies (UCHL1, 4KB5 and L26) recognizing different lymphocyte antigens. LNs were found in 35% of cases of idiopathic thrombocythaemia, 24.6% of myelofibrosis/osteomyelosclerosis, 18.2% of polycythaemia vera 12.1% of chronic myeloid leukaemia and 19.2% of borderline cases. Varying degrees of immunohistochemical positivity for the three antibodies tested were found. LNs were always made up of variable proportions of both T- and B-lymphocytes with a prevalence of T-cells. This latter observation suggests that bone marrow LNs in CMPDs could be an expression of reactivity.

Bone marrow trephine interpretation: diagnostic utility and potential pitfalls

Good quality paraffin-embedded sections can be obtained from bone marrow trephines, allowing the routine use of these biopsies in diagnostic histopathology. Trephines are superior to aspirates, especially for the assessment of marrow cellularity, the extent and pattern of tumour infiltration and the cell type. Bone marrow biopsies are useful in several areas, e.g. non-haematological disorders, myelodysplasia, the myeloproliferative group, lymphomas and leukaemias, which are briefly discussed below. Further advances in interpretation are likely with more frequent use of bone marrow trephines.

Dysmegakaryopoiesis in myelodysplastic syndromes (MDS): an immunomorphometric study of bone marrow trephine biopsy specimens

An immunohistochemical and morphometric analysis was performed on trephine biopsy specimens of the bone marrow in 40 patients (23 men and 17 women, mean age 62 years) with different subtypes of myelodysplastic syndromes (MDS) to determine dysmegakaryopoiesis, but particularly precursor cells--that is, pro- and megakaryoblasts. In 31 of the 40 patients the numbers of megakaryocytes were increased which was associated with a predominance of smaller cell forms (micromegakaryocytes). Compared with periodic acid Schiff, immunostaining with a formalin resistant monoclonal antibody against glycoprotein IIIa (Y2/51(CD61) showed a clinically important proportion of immature elements. These could be designated pro- and megakaryoblasts by taking morphometric measurements on smears and bone marrow sections. There was a relevant increase in the number of promegakaryoblasts in 32 patients, consistent with uncontrolled expansion of the precursor pool. Seventeen repeated bone marrow biopsy specimens taken after chemotherapy largely showed a decrease in the numbers of megakaryocytes including the precursor cell population. Moreover, morphometric evaluation disclosed that micromegakaryocytes in MDS differ significantly from those in chronic myeloid leukaemia (CML) due to distinctive nuclear features and a disturbed nuclear:cytoplasmic ratio. These changes generate a more pleomorphic or atypical appearance of this cell population in MDS, compared with micromegakaryocytes in CML. It is concluded that the disproportionate increase in megakaryocyte precursors and the grossly abnormal aspects of micromegakaryocytes in MDS are characteristics of the severe defect involving haematopoiesis in this disorder.

Chronic myeloproliferative disorders: prognostic importance of new working classification

Variants of chronic myeloproliferative disorders (CMPD) were compared according to their clinical features and classified by bone marrow biopsy appearances. Subsequently, this classification was further evaluated using survival data and histological variables from iliac crest biopsy specimens of an additional 1391 patients, making a total of 2241 patients available for analysis of outcome. The patients were grouped again into three main classes: "typical"; "variant"; and "transformed". "Typical" comprised the "classic" groups. "Variant" included the less uniform myeloproliferative syndromes, distinguished also by more variable clinical features, a different prognosis, and a greater tendency to fibrotic and blastic transformation. "Transformed" defined the end stages of both "typical" and "variant" types. Ten subgroups were distinguished by different histology and prognosis. Particular prognostic importance was assigned to atypia and immaturity of haemopoiesis, predominance of individual haemopoietic cell line, number and anomalies of megakaryocytes and progressive fibrosis. It is suggested that the proposed subclassification would be helpful for studies of epidemiology and therapeutic trials by allowing more homogeneous groups to be recognised.

Comparison of bone marrow histology in early chronic granulocytic leukemia and in leukemoid reaction

A retrospective study was performed on bone marrow biopsies of 50 untreated patients with leukemoid reactions (LR) and 50 untreated patients with early chronic granulocytic leukemia (CGL). A comparison was made between hematopoietic and adipose tissues, bone and its cells, as well as other stromal components in these two disorders. Histologic and histomorphometric analyses revealed significant differences in trabecular structure, in localization of fat cells, in numbers of sinusoids, capillaries and various stromal elements. No significant differences between LR and CGL were detected in the quantity of erythro- and granulocytopoiesis and of megakaryocytes, but these were smaller in CGL than in LR. This histologic and histomorphometric evaluation demonstrates that certain histologic features may serve as valuable aids in distinguishing LR from CGL.

Chronic myeloproliferative disorders in bone marrow biopsies

This Diagnostic Seminar intends to announce that CMPDs can be classified from BMB histologically by a rather simple system, which can be applied by interested histopathologists successfully. The rationale of this classification is to stay within the groups of diseases which are outlined by clinical findings including the peripheral blood and bone marrow smears. The concept of traditional classification as given by the WHO and textbooks, however, has to be revised as follows (1) Primary diseases of CMPDs must be distinguished from advanced disorders. Primary diseases are CML, P. vera, Thrombocythemia, CMGM, and unclassifiable CMPD. (2) Idiopathic, primary myelosclerosis of the bone marrow is a reactive feature consecutive to neoplastic transformation of hematopoiesis, i.e. myeloproliferation. (3) Advanced disorders comprise (3.1.) excess of blasts and blast crisis, and (3.2.) early myelosclerosis, myelosclerosis and myelofibrosis, advanced myelofibrosis. Advanced disorders are designated by a composed term classifying them among the groups of primary disease and specifying the advanced stage by a suffix, so that the underlying disease remains coining the term, even in unclassifiable cases in which only CMPDs can be applied. (4) The CML group must be subtyped into CML of common type versus that with increase or predominance of megakaryocytes. By this system of classification, it seems possible to classify and type the spectrum of variations occurring among CMPDs to a satisfying result.

An immunomorphometric study on megakaryocyte precursor cells in bone marrow tissue from patients with chronic myeloid leukemia (CML)

An immunomorphometric study was performed on trephine biopsies of the bone marrow in 41 patients with chronic myeloid leukemia (CML) to determine number and size of megakaryocytic precursor cells (pro- and megakaryoblasts). For specific staining, a monoclonal antibody against platelet glycoprotein IIIa (Y2/51) was employed which is applicable on routinely fixed and paraffin embedded tissue. In comparison with control specimens from 15 patients, in CML morphometric analysis revealed an increase in the total amount of megakaryocytes per square and cubic millimeter marrow tissue, but particularly in patients with thrombocythemia. Moreover, a non-disorderly expansion of the megakaryocyte precursor pool was recognizable by showing a relative frequency of pro- and megakaryoblasts in congruence with the normal value. In this context a significant correlation between the counts for Y2/51-positive megakaryocytic elements and promegakaryoblasts with the corresponding platelet values was encountered. The more mature stages of megakaryopoiesis (pro- end megakaryocytes) disclosed a relevant shift to smaller cell forms with rounded cell perimeters and a more compact aspect of their nuclei. Additionally, in 6 patients with CML, evolution into a subacute and manifest (micro)-megakaryoblastic transformation accompanied by myelofibrosis could be demonstrated by a retrospective review of file material.

Analysis of bcr rearrangements in primary (essential) thrombocythaemia

A clinical and molecular study was performed on 10 patients with the presumptive diagnosis of primary thrombocythaemia (PTH). In all cases conspicuous megakaryocytic proliferation in bone marrow smears was detected in the absence of the Philadelphia chromosome (Ph1), elevated red blood cell mass and evidence for a reactive cause of the thrombocytosis. We analyzed whether rearrangements of the bcr gene occurred in untreated patients. Bcr rearrangements were detected in the bone marrow cells but not in peripheral blood bells of one patient, indicating that this case might be related at the molecular level with Philadelphia chromosome negative CML, in which bcr rearrangements could be demonstrated.

Agnogenic myeloid metaplasia (AMM)--correlation of bone marrow lesions with laboratory data: a longitudinal clinicopathological study on 114 patients

A clinicopathological study was performed on 114 patients (46 male/68 female, median age 67 years) with the diagnosis of agnogenic myeloid metaplasia (AMM) respectively primary osteo-myelofibrosis which was not preceded by any other or allied subtype of chronic myeloproliferative disorders. On admission patients revealed a striking variability of laboratory data as well as different histopathological features of initial bone marrow biopsies. For this reason discrimination was done into two groups based on bone marrow findings: group I patients (n = 46, 19 male/27 female) showed a hypercellular marrow without or only borderline (n = 24) to slight (n = 22) reticulin fibrosis and group II cases (n = 68, 27 male/41 female) displayed coarse bundles of collagen fibres (n = 18) frequently accompanied by osteosclerosis (n = 50). Statistical analysis of the corresponding initial hematological findings resulted in significant differences. These differences concerned also the complications occurring during the lengthy course of disease, which included a higher incidence of pancytopenia and severe marrow failure with hemorrhage and blast crisis in group II patients. However, overall survival time was not different in both groups. This may be related to the similarity of age distribution (64 resp. 65 years) and its significant association with arteriosclerotic vascular lesions. Consequently acute myocardial infarction and congestive heart failure were frequent causes of death in addition to infections due to marrow failure and blast crisis. Repeated bone marrow biopsies in 24 patients revealed an insidious transition from hypercellular lesions (group I) into advanced fibro-osteosclerotic changes (group II) concurring with laboratory data. Therefore our discrimination into two groups of patients represents variable stages or static histological and corresponding hematologic features in the evolution of a dynamic disease process in AMM.