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

Philadelphia chromosome-negative chronic myeloproliferative disease

Session 2 of the 2007 Workshop of the Society for Hematopathology/European Association for Haematopathology was focused on Philadelphia chromosome-negative chronic myeloproliferative diseases (Ph- MPDs), recently termed chronic myeloproliferative neoplasms. The presented and submitted cases highlighted some important issues and also impending problems associated with the diagnosis and classification. Cases included predominantly rare entities like chronic eosinophilic leukemia and related disorders, chronic neutrophilic leukemia, and others with specific genetic abnormalities that allowed molecularly targeted therapy. In this context, the distinctive role of a positive JAK2(V617F) mutation for the diagnosis of Ph- MPD was underscored, including entities with a low allele burden and the discrimination from reactive disorders (autoimmune myelofibrosis, reactive thrombocytosis). Although novel genetic and molecular approaches have significantly improved the way we classify Ph- MPD, a combined clinicopathologic approach, including representative bone marrow specimens, still remains the yardstick for diagnosis.

Osteomyelosclerosis with thalassemia trait: report of a rare association, study of platelet function tests and review of literature

Idiopathic myelofibrosis is a chronic myeloproliferative disorder characterized by excessive connective tissue deposition in the bone marrow. It presents with leucoerythroblastic anemia and massive splenomegaly. It is termed osteomyelosclerosis in the presence of primitive bone formation in the bone marrow and radiological presence of osteosclerosis. A 40-year-old male, known case of thalassemia trait presented with fatigue and lump in the abdomen for two months. Physical examination showed splenomegaly 8.5 cm below costal margin. X-ray examination revealed multiple osteosclerotic lesions involving the pelvis and long bones. Hemogram showed: hemoglobin 7.8 gm/dl, TLC 47,500/mm(3); DLC was polymorphs 49%, lymphocytes 7%, eosinophils 4%, basophils 4%, blasts 5%, promyelocytes 2%, myelocytes 14%, metamyelocytes 10%. Platelet count was 60,000/mm(3). Peripheral blood film showed leucoerythroblastic blood picture with features of dysmyelopoiesis. Bone marrow aspiration was diluted with peripheral blood. Bone marrow biopsy showed replacement of marrow by grade III reticulin fibrosis. Bony trabaculae were wide and thick. Platelet function studies were abnormal. The clinical, radiological and hematological features suggested a diagnosis of osteomyelosclerosis. We present this case because no similar association of osteomyelosclerosis with thalassemia trait has been described in English literature to date. This is the first study from India, which describes platelet function tests in a patient with osteomyelosclerosis.

Bone marrow histopathology in the diagnosis of chronic myeloproliferative disorders: A forgotten pearl

Histopathology of bone marrow (BM) biopsies plays a crucial role in the interdisciplinary approach to diagnosis and classification of chronic myeloproliferative disorders (CMPDs). Based on careful clinicopathologic studies, BM features are critical determinants that help to predict overall prognosis, to detect complications such as progression to myelofibrosis and blast crisis, and to assess therapy-related changes. A systematic evaluation of BM histopathology allows an objective identification of cases of (true) essential thrombocythemia (ET) and their separation from (false) ET, which often is the prodromal stage of chronic idiopathic myelofibrosis (CIMF). By follow-up examinations that include BM biopsies, the progression of the disease process is unveiled, which is especially important for patients with initial (early) polycythemia vera and prefibrotic CIMF that may require a different therapeutic approach than the full-blown stages. In conclusion, BM biopsy should be considered as major diagnostic tool for evaluation and follow-up of patients enrolled in prospective studies.

A critical reappraisal of the WHO classification of the chronic myeloproliferative disorders

Following the introduction of the WHO classification of chronic myeloproliferative disorders (MPDs), after approximately 5 years, a critical reappraisal appears to be warranted. Retrospective clinico-pathological evaluations conducted in the meantime, as well as the detection of new biomarkers, may aid in testing the validity of these new criteria. Based on a large series of patients with chronic myeloid leukemia (CML), an analysis of bone marrow (BM) features and risk classifications revealed that the fiber content exerted a most important and independent impact on prognosis. This finding was also supported in a prospective randomized study and therefore myelofibrosis should be included in any staging system in CML related to survival. Moreover, it is important to emphasize the dynamics of the disease process in MPDs, especially in polycythemia vera (PV) and chronic idiopathic myelofibrosis (CIMF). Latent-stage PV is difficult to recognize when adhering to the proposed limits for hemoglobin (or red cell mass) without regarding the erythropoietin (EPO) level, endogenous erythroid colonies (EECs) or BM histopathology. Initial PV may firstly present with complications and, when accompanied by a high platelet count, mimics essential thrombocythemia (ET). Consequently, BM morphology and EPO level should be entered as major diagnostic criteria for PV. To document more accurately the progress of disease, a simplified scoring system concerning myelofibrosis has to be included in the histological description of CIMF. The diagnostic guidelines of BM features in ET should be improved because, usually, there is neither a significant proliferation nor left-shifting of the granulo- and erythropoiesis detectable and no relevant increase in reticulin. A comparison of clinical data and BM morphology reveals that biomarkers (EPO, EECs, PRV-1, JAK2) show an overlapping pattern of positivity between the different subtypes of MPDs.

Bone marrow changes in chronic myelogenous leukaemia after long-term treatment with the tyrosine kinase inhibitor STI571: an immunohistochemical study on 75 patients

AIMS

To carry out an immunohistochemical study on bone marrow (BM) biopsy specimens in 75 patients with chronic myelogenous leukaemia (CML) on long-term STI571 therapy.

METHODS AND RESULTS

Sequential BM specimens taken at intervals of 21 +/- 6 months were investigated by enzyme- and immunohistochemistry including proliferating cell nuclear antigen and apoptosis. Evaluation was performed either by semiquantitative scoring or by morphometry (CD61+ megakaryopoiesis). In 41 patients with chronic phase CML, treatment resulted in a significant decrease in cellularity and neutrophil granulopoiesis contrasting with an accumulation of erythroid precursor cells. Morphometry showed a reduction of abnormal micromegakaryocytes consistent with normalization. Regression of myelofibrosis was identified in eight of 15 patients, whereas progression occurred in 17 patients; mostly in those with acceleration and blastic crisis. The increased post-treatment incidence of reactive lymphoid nodules was remarkable. Myeloblasts, CD34+ progenitors and immature myelomonocytic cells initially decreased, but recurred in 14 patients who later developed a relapse. STI571 exerted an inhibitory effect on cell proliferation associated with enhanced apoptosis in responding patients.

CONCLUSION

Long-term treatment with STI571 exerts pronounced changes on BM histopathology that not only involve haematopoiesis and stromal constituents, but also proliferation and apoptosis.

Bone marrow features of diagnostic impact in erythrocytosis

Controversy continues to persist about the role of histopathology regarding diagnosis of polycythemia vera (PV). For this reason, a clinicopathological study was performed on 334 patients presenting with a sustained borderline to marked erythrocytosis (hemoglobin >17 g/dl in men and >15 g/dl in women). The aim was to elucidate the discriminating impact of bone marrow biopsy examinations in an independent fashion from laboratory parameters. According to morphological findings based on a semiquantitative evaluation of standardized features, cellularity, megakaryocytes (quantity, size, pleomorphous aspect, clustering, nuclear lobulation), eosinophils, cellular debris, perivascular plasmacytosis and iron-laden macrophages exerted a distinctive value. Comparison with clinical data and follow-up revealed that in only 13 patients (4%), histopathology failed to differentiate clearly between PV (208 patients) and secondary polycythemias (113 patients). In conclusion, certain sets of morphological parameters allow a distinction between autonomous and reactive polycythemias and therefore enhance significantly diagnostic validity.

Megakaryocyte features and bcr/abl translocation in chronic myeloid leukemia following imatinib mesylate (STI571) therapy--a fluorescence in-situ hybridization study

Following therapy with imatinib (STI571) hematologic and cytogenetic response in chronic myeloid leukemia (CML) is associated with conspicuous alterations of bone marrow (BM) morphology. Besides reduction of cellularity and fibrosis, small megakaryocytes characteristic for this disorder were replaced by large, normally appearing cells of this lineage. However, it is not known whether and to which extent these changes are accompanied by a loss of the bcr/abl translocation. Therefore an immunohistochemical (CD61) and fluorescence in-situ hybridization (FISH) study was performed on sequential BM biopsies in 5 patients with CML receiving STI571 without any pretreatment. Morphometric analysis revealed that the prevalent population of 47% micromegakaryocytes (size < or = 150 microm2) was significantly reduced (15%) during therapy and that a conspicuous shift to medium-sized and large megakaryocytes occurred. According to FISH analysis in the initial BM biopsy sections 71% of all myeloid cells exhibited the bcr/abl gene and concerning megakaryopoiesis about 65% of the prominent micromegakaryocytes displayed positive signals. After treatment this peculiar cell population decreased significantly while the emerging large megakaryocytes (52%) totally lacked a bcr/abl labeling. Because cytogenetic response and reduction of micromegakaryocytes seem to be linked, this feature may be useful to monitor therapeutic efficacy by evaluating BM morphology.

Regression der Philadelphia-Chromosom (bcr/abl)-positiven Myelo- und Megakaryopoiese unter Imatinib(STI571)-Therapie bei chronischer myeloischer Leuk�mie (CML)

In chronic myeloid leukemia following therapy with Imatinib (STI571) hematologic and cytogenetic response is associated with conspicuous changes of bone marrow morphology. However, it is not known to which extent these alterations are accompanied by a loss of the bcr/abl translocation. To study regression of the leukemic cell population we recruited 14 patients lacking pretreatment. Therapy resulted in a reduction of CD61(+) megakaryopoiesis. Dwarf megakaryocytes characteristic for this disorder were replaced by large, normally appearing cells of this lineage. Morphometric analysis confirmed the significant decrease in the number of micromegakaryocytes and yielded planimetric parameters in keeping with normalization. Moreover, a fluorescence in-situ hybridization study in five patients of this cohort revealed that before therapy 70% of all myeloid cells exhibited the bcr/abl gene. Regarding megakaryopoiesis about 65% of the micromegakaryocytes displayed positive signals. Following treatment these bcr/abl(+) cell populations decreased significantly while the emerging large megakaryocytes lacked a proper labeling. Because cytogenetic response and reduction of atypical micromegakaryocytes are linked, this feature may be useful to monitor therapeutic efficacy.

Follow-up examinations including sequential bone marrow biopsies in essential thrombocythemia (ET): a retrospective clinicopathological study of 120 patients

Diagnosis of essential thrombocythemia (ET) has been usually established by regarding the criteria of the Polycythemia Vera Study Group. Accordingly, a retrospective clinicopathological study was performed on 120 patients with a follow-up ranging between 5 and 13 years and repeated bone marrow trephine examinations. Following the new WHO classification, at presentation patients revealed three distinctive patterns of bone marrow (BM) features: (true) ET in 43 patients, prefibrotic idiopathic myelofibrosis (IMF) in 50 patients, and early IMF in 27 patients. Heterogeneity of morphological features was associated with correspondingly expressed laboratory data. Contrasting initial and early IMF, patients with true ET displayed an about 80% probability to lack splenomegaly, anemia, and increase in the LDH and LAP values and also failed to show any myeloblasts or erythroblasts on the peripheral blood films. Follow-up examinations including sequential BM biopsies (mean interval 39 +/- 31 months) disclosed that of the 43 patients with true ET only one developed an increase in reticulin. On the other hand, 65 of 77 patients with prefibrotic and early IMF evolved into overt myelofibrosis-osteosclerosis. Moreover, survival analysis demonstrated significant differences in our patients. A neglectable proportion of life loss according to a sex- and age-matched general population was found in true ET (less than 11%) opposed to IMF without or mild fibrosis (range 21% to 32%).

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.

Idiopathic erythrocytosis, diagnosis and clinical management

By definition, idiopathic erythrocytosis (IE) applies to a group of patients characterised by having a measured RCM above their predicted normal range (an absolute erythrocytosis) and following investigation do not have a form of primary or secondary erythrocytosis. Patients with IE are heterogenous. The possibilities include physiological variation, 'early' polycythaemia vera (10-15% develop clear features of PV over a few years), unrecognized congenital erythrocytosis, unrecognized or unrecognizable secondary acquired erythrocytosis or a currently undescribed form of primary or secondary erythrocytosis. Patients are more commonly male with a median age at presentation of 55-60 years. Approximately half of the patients present with vascular occlusive complications. Retrospective evidence indicates that vascular occlusion occurs less frequently when the PCV is controlled at normal levels. Venesection is the treatment of choice to lower the PCV. As a general approach to management, all patients with a PCV above 0.54 should be venesected to a PCV less than 0.45. This target PCV should also apply to patients with lesser degrees of raised PCV who have additional other risk factors for vascular occlusion.

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.

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.

Therapy-related changes of CD20+ and CD45RO+ lymphocyte subsets in chronic myeloid leukemia (CML): an immunohistochemical and morphometric study on sequential trephine biopsies of the bone marrow

Little information exists about the amount of CD45RO+-T- and CD20+-B-lymphocytes in the bone marrow of patients with Philadelphia chromosome-positive chronic myelogenous leukemia (Ph1+-CML) at presentation or regarding corresponding changes during therapy. On the other hand, quantification of this cell compartment seems to be imperative for two reasons: first, the presumed association of immunocompetent lymphocyte subsets in the expansion of the leukemic cell clone; and second, a speculated relationship with the complex generation of myelofibrosis. Therefore, an immunohistological and morphometric study was performed on 219 representative trephine biopsies of the bone marrow derived from 70 patients with repeated examinations during the course of Ph1+-CML. For the identification of the different lymphocyte populations, the monoclonal antibodies UCHL-1 (CD45RO) and L26 (CD20) were applied on formaldehyde-fixed and decalcified specimens. In comparison to a control group and calculated per hematopoietic cells, the CML bone marrow showed about a 50% decrease in the total amount of lymphocytes. Determination of CD45RO+ and CD20+ subsets revealed a significant enhancement during treatment. Because of the different intervals (range, 10 to 25 mo) between first and last biopsy in the various therapeutic groups, results had to be modified by considering dynamic features. This calculation included changes of the lymphocyte subpopulations related to time. Contrasting the CD45RO+ lymphocytes, a relevant increase in the CD20+ subset could be observed after interferon-a treatment or corresponding combination regimens. No significant correlations were found between fiber density at onset (first biopsy) or development of fibrosis and lymphocyte proliferations in the course of CML. Our results are in keeping with the finding that a proper immune response consistent with an increased lymphocyte growth seems to be associated with a regression of the clonally-transformed cell population. Opposed to a repeatedly discussed pathomechanism, we failed to demonstrate any quantitative relationships between the extent of lymphocyte proliferations and occurrence or progression of myelofibrosis.

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.

Focal lymphoid aggregates (nodules) in bone marrow biopsies: differentiation between benign hyperplasia and malignant lymphoma--a practical guideline

AIMS

To provide practical guidelines for the differentiation between benign and malignant focal lymphoid aggregates (lymphoid nodules) in routinely referred bone marrow trephine biopsies, using a synoptic approach including clinical data and histological workup.

METHODS

For easy identification of very small lymphoid infiltrates the chloroacetate esterase stain was applied as a screening procedure. This allowed the identification of 491 formalin fixed, paraffin wax embedded specimens with one or more lymphoid nodules. Examination of lymphoid infiltrates included such variables as histotopography, demarcation, cytology, reticulin fibres, and immunohistochemistry with a set of monoclonal antibodies (CD20, CD45R, CD45R0, CD3, CD43). Evaluation of clinical and morphological data was carried out independently. In case of malignant lymphomas, a correlation with corresponding lymph node findings was made.

RESULTS

352 patients had benign focal lymphoid aggregates usually associated with systemic autoimmune diseases, chronic myeloproliferative disorders, toxic myelopathy, and viral infections. Discrete nodular infiltrates of (small cell) malignant lymphomas (n = 93) simulating benign hyperplasia were found in chronic lymphocytic leukaemia, germinal centre cell lymphomas (CB-CC), and lymphoplasmacytic/cytoid lymphomas (LPI). In addition to immunoreactivity, certain histological variables proved distinctive. These were: (1) histotopography, that is, localisation of the lymphoid aggregates within the bone marrow space; (2) relation to the surrounding tissue: margination or interstitial spillage of lymphoid cells; and (3) increase in reticulin fibres.

CONCLUSIONS

A combined diagnostic procedure identifying several distinctive features, in particular histotopography and immunohistochemistry, provides a most promising way of discriminating reactive from neoplastic lymphoid nodules in the bone marrow.

Diagnosis and classification of erythrocytoses and thrombocytoses

An erythrocytosis describes an increased peripheral blood packed cell volume (PCV) and is deemed to be absolute or apparent depending on whether or not the measured red cell mass (RCM) is above the reference range. This reference range must be related to the individual's height and weight to avoid erroneous interpretations using ml/kg total body weight expressions in obesity. Absolute erythrocytoses are divided into primary, where the erythropoietic compartment is intrinsically abnormal, secondary, where the erythropoietic compartment is normal but is responding to external pathological events leading to an increased erythropoietin drive, and idiopathic, where neither a primary nor a secondary erythrocytosis can be established. Both primary and secondary erythrocytoses have congenital and acquired forms. The only form of primary acquired erythrocytosis that has been defined is the clonal myeloproliferative disorder, polycythaemia vera (PV). Modified diagnostic markers for PV are proposed. Thrombocytoses can be classified into primary, where megakaryopoiesis is intrinsically abnormal, secondary, where megakaryopoiesis is normal but increased platelet production is a reaction to some other unrelated pathology, and finally idiopathic. This latter new group would be used for patients not satisfying the criteria for primary or secondary thrombocytoses, if these were more precise and rigidly used than currently is the case. While theoretically congenital and acquired forms of primary and secondary thrombocytoses might exist, only one cause of secondary congenital thrombocytosis has been established, and primary congenital thrombocytosis has not yet been precisely defined. Primary (essential) thrombocythaemia (PT) is one of the forms of primary acquired thrombocytoses. The diagnostic criteria of PT traditionally involve the exclusion of secondary thrombocytoses and other myeloproliferative disorders but marrow histology could hold a key positive diagnostic role if objective histological features of PT were agreed.

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.

Classification and staging of Ph-negative myeloproliferative disorders by histopathology from bone marrow biopsies

The present study illustrates characteristic features of histopathology in the 3 non-leukemic, Ph-negative groups of chronic myeloproliferative diseases (CMPD). Attention is paid to the final outcome of CMPD, especially its transformation into acute leukemias and the occurrence of myelofibrosis from bone marrow biopsies (BMB) in a total of 1,716 CMPD patients. Essential thrombocythemia (ET), polycythemia vera (P. vera), and chronic megakaryocytic granulocytic myelosis (CMGM) can readily be distinguished by histopathology from BMB in the great majority of patients without regarding laboratory data, leaving a compartment of about 12% unclassifiable cases. Histologic patterns of staging are the increase in number and pleomorphism of megakaryocytes (MK), increase in number and density of reticulin fibers and collagen fibrosis, and excess of blasts. These 3 criteria are each graded from 0 to 3 in every biopsy. From these, a staging results by means of the histology of BMB in each of the Ph-negative CMPD. This staging provides a classification by defined criteria which permits comparative studies, the possibility of monitoring the individual patients by follow-up histology, and offers a baseline for reliable evaluation of results from therapy protocols.

Aspirin in polycythemia vera and essential thrombocythemia: current facts and perspectives

The role of aspirin in the antithrombotic strategy of patients with polycythemia vera (PV) and essential thrombocythemia (ET) is highly controversial. Long considered unsafe on the basis of a single clinical trial testing very high doses in PV patients, aspirin is being increasingly used at lower dosage. The rationale for the use of aspirin in patients with PV and ET is provided by the efficacy of this agent in the treatment of microcirculatory disturbances of thrombocythemic states associated with myeloproliferative disorders and by recent evidence that asymptomatic PV and ET patients have persistently increased thromboxane (TX) A2-biosynthesis. This increase, which most likely reflects enhanced platelet activation in vivo, is independent of the platelet mass and blood viscosity and largely supressed by a short term low-dose aspirin regimen (50 mg/day for 7 days). Since enhanced TXA2 biosynthesis may play a role in transducing the increased thrombotic risk associated with PV and ET, long-term low-dose aspirin administration has been proposed as a possible antithombotic strategy in these subjects. The safety of this treatment in PV patients has been recently reassessed by the Gruppo Italiano per lo Studio della Policitemia Vera (GISP) which has followed for over one year 112 patients randomized to receive 40 mg/day aspirin or placebo. In the same study, serum TXB2 measurements provided evidence that the low-dose aspirin regimen tested was fully effective in inhibiting platelet cyclooxygenase activity. On this basis, a large scale trial aimed at assessing the antithrombotic efficacy of this approach is currently being organized. In patients with ET both the minimal aspirin dose required for complete inhibition of platelet cyclooxygenase and the safety of long-term aspirin administration need to be established prior to extensive clinical evaluation of this strategy.

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.

Clinical and histological features retain their prognostic impact under interferon therapy of CML: a pilot study

In 55 patients with Ph1+ CML under interferon (IFN) monotherapy, an immunohistochemical and morphometric study on pretreatment bone marrow biopsies was performed to evaluate the prognostic impact of clinical as well as histological disease features. For identification of megakaryocytes we used the PAS stain and CD61 to calculate the subfraction of precursors (pro- and megakaryoblasts). Demonstration of macrophages and their different subsets was carried out by PG-M1 (CD68) and the GSA-1 lectin. The erythroid precursors were stained by Ret40f (anti-glycophorin C). Density of argyrophilic (reticulin plus collagen) fibers was determined by applying Gomori's silver impregnation method. Clinical variables like state of hematological response to IFN administration, age, spleen and liver size, myeloblasts plus promyelocytes, basophils as well as basophils and eosinophils exerted a predictive capacity by univariate statistical analysis. However, when entering these factors into previously published risk models, i.e., the so-called Sokal score and its modifications, to assess subgroups with different survival patterns or relative risk groups, a clear-cut discrimination was not feasible. Bone marrow features of prognostic value consisted of megakaryocytes and their precursors, fibers, and pro- and erythroblasts. Only when including histological variables into a formerly reported Cox model, could a significant separation of patients into the different categories or relative risk groups be computated. In conclusion, the present data emphasize the prognostic impact of histological parameters to be considered in all clinical trials on CML.

Bone marrow and serum connective tissue polypeptides in idiopathic myelofibrosis

The distribution of collagen type VI and tenascin has been determined in both normal and myelofibrotic bone marrow by immunohistological techniques. In normal sections positivity was demonstrated in the periosteum (collagen type VI and tenascin) and in the walls of small blood vessels (tenascin). In contrast, myelofibrotic bone marrow showed an increased deposition of both proteins, especially collagen type VI, although this increase was restricted to the later fibrotic stages of the disease. Serum concentrations of collagen type I (PICP), collagen type III (PIIIP) and laminin (laminin P1) related polypeptides were determined in a further 26 patients. PIIIP levels were significantly raised, in contrast to PICP and laminin P1 concentrations. All three markers, however, were significantly elevated in patients with active/transforming disease. Laminin P1 and PICP levels showed a strong correlation, indicating a relationship between basement membrane and interstitial collagen metabolism, although they do not appear to offer any advantage over PIIIP for the monitoring of disease activity.