Chronic myeloproliferative disorders in bone marrow biopsies

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

Simple Summary

Myeloproliferative neoplasms (MPNs) are clonal hematological disorders, characterized by increased proliferation of the myeloid lineages in the bone marrow. Since their original recognition by William Damashek in 1951, MPNs have been extensively investigated at a clinical-pathological and molecular level. This prompted a progressive refinement of their classification and diagnostic criteria. Uncertainties nonetheless remain in a small (yet consistent) subset of cases, characterized by unconventional and/or overlapping clinical-pathological features. Such cases (referred to as MPN, unclassifiable [MPN-U]) encompass a broad spectrum of entities, including early phase MPNs, terminal (i.e., fibrotic) MPNs, MPNs associated with inflammatory or neoplastic disorders, and poorly characterized MPNs with clinical-pathological mismatch or atypical molecular features. In this review, we discuss the rationale behind the classification and diagnostic criteria of MPNs, focusing on the still open issues concerning MPN-U.

Abstract

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.

Assessment of the Number and Phenotype of Macrophages in the Human BMB Samples of CML

Macrophages have emerged as a key player in tumor biology. However, their number and phenotype in human bone marrow of biopsy (BMB) samples of chronic myeloid leukemia (CML) and their association with disease progression from an initial chronic phase (CP) to accelerated phase (AP) to advanced blast phase (BP) are still unclear. BMB samples from 127 CML patients and 30 patients with iron-deficiency anemia (IDA) as control group were analyzed by immunohistochemistry. The expression levels of CD68, CD163, and CD206 in BMB samples of CML patients were significantly higher than those in the patients of control group (P < 0.01), and we observed that their positive expression was gradually elevated during the transformation of CML-CP to AP to BP (P < 0.01). However, the expressions of CD68, CD163, and CD206 in released group were downregulated and contrasted to these in control group; there exists statistical significance (P < 0.01). The percentage ratio of CD163 and CD206 to CD68 was pronounced to be increasing from CML-CP to AP to BP (P < 0.01). Hence, the higher proportion of CD68⁺, CD163⁺ and CD206⁺ macrophages in BMB samples can be considered a key factor for disease progression of CML patients. Targeting macrophages, especially the M2 phenotype may help in designing therapeutic strategies for CML.

European vs 2015-World Health Organization clinical molecular and pathological classification of myeloproliferative neoplasms

The BCR/ABL fusion gene or the Ph¹-chromosome in the t(9;22)(q34;q11) exerts a high tyrokinase acticity, which is the cause of chronic myeloid leukemia (CML). The 1990 Hannover Bone Marrow Classification separated CML from the myeloproliferative disorders essential thrombocythemia (ET), polycythemia vera (PV) and chronic megakaryocytic granulocytic myeloproliferation (CMGM). The 2006-2008 European Clinical Molecular and Pathological (ECMP) criteria discovered 3 variants of thrombocythemia: ET with features of PV (prodromal PV), “true” ET and ET associated with CMGM. The 2008 World Health Organization (WHO)-ECMP and 2014 WHO-CMP classifications defined three phenotypes of JAK2^V617F mutated ET: normocellular ET (WHO-ET), hypercelluar ET due to increased erythropoiesis (prodromal PV) and ET with hypercellular megakaryocytic-granulocytic myeloproliferation. The JAK2^V617F mutation load in heterozygous WHO-ET is low and associated with normal life expectance. The hetero/homozygous JAK2^V617F mutation load in PV and myelofibrosis is related to myeloproliferative neoplasm (MPN) disease burden in terms of symptomatic splenomegaly, constitutional symptoms, bone marrow hypercellularity and myelofibrosis. JAK2 exon 12 mutated MPN presents as idiopathic eryhrocythemia and early stage PV. According to 2014 WHO-CMP criteria JAK2 wild type MPL⁵¹⁵ mutated ET is the second distinct thrombocythemia featured by clustered giant megakaryocytes with hyperlobulated stag-horn-like nuclei, in a normocellular bone marrow consistent with the diagnosis of “true” ET. JAK2/MPL wild type, calreticulin mutated hypercellular ET appears to be the third distinct thrombocythemia characterized by clustered larged immature dysmorphic megakaryocytes and bulky (bulbous) hyperchromatic nuclei consistent with CMGM or primary megakaryocytic granulocytic myeloproliferation.

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.

PVSG and WHO vs European Clinical, Molecular and Pathological Criteria for prefibrotic myeloproliferative neoplasms

The Polycythemia Vera Study Group (PVSG), World Health Organization (WHO) and European Clinical, Molecular and Pathological (ECMP) classifications agree upon the diagnostic criteria for polycythemia vera (PV) and advanced primary myelofibrosis (MF). Essential thrombocythemia (ET) according to PVSG and 2007/2008 WHO criteria comprises three variants of JAK2^V617F mutated ET when the ECMP criteria are applied. These include normocellular ET, hypercellular ET with features of early PV (prodromal PV), and hypercellular ET due to megakaryocytic, granulocytic myeloproliferation (ET.MGM). Evolution of prodromal PV into overt PV is common. Development of MF is rare in normocellular ET (WHO-ET) but rather common in hypercellular ET.MGM. The JAK2^V617F mutation burden in heterozygous mutated normocellular ET and in heterozygous/homozygous or homozygous mutated PV and ET.MGM is of major prognostic significance. JAK2/MPL wild type ET associated with prefibrotic primary megakaryocytic and granulocytic myeloproliferation (PMGM) is characterized by densely clustered immature dysmorphic megakaryocytes with bulky (bulbous) hyperchromatic nuclei, which are never seen in JAK2^V617F mutated ET, and PV and also not in MPL⁵¹⁵ mutated normocellular ET (WHO-ET). JAK2^V617 mutation burden, spleen size, LDH, circulating CD34⁺ cells, and pre-treatment bone marrow histopathology are mandatory to stage the myeloproliferative neoplasms ET, PV, PMGM for proper prognosis assessment and therapeutic implications. MF itself is not a disease because reticulin fibrosis and reticulin/collagen fibrosis are secondary responses of activated polyclonal fibroblasts to cytokines released from the clonal myeloproliferative granulocytic and megakaryocytic progenitor cells in ET.MGM, PV and PMGM.

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.

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.

Classification of Ph-Negative Chronic Myeloproliferative Disorders – Morphology as the Yardstick of Classification

OBJECTIVE

Histopathology of bone marrow (BM) biopsies plays a crucial role in the interdisciplinary approach to diagnosis and classification of Ph-negative chronic myeloproliferative disorders. 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.

METHODS AND RESULTS

A systematic evaluation of BM histopathology allows an objective identification of cases of (true) essential thrombocythemia and their separation from early prefibrotic stages of chronic idiopathic myelofibrosis. By follow-up examinations that include BM biopsies, the progression of the disease process is unveiled, which is especially important for patients with initial polycythemia vera and prefibrotic chronic idiopathic myelofibrosis that may require a different therapeutic approach than the full-blown stages.

CONCLUSION

BM biopsy should be considered as major diagnostic tool for evaluation and follow-up of patients enrolled in prospective studies.

Essential thrombocythemia or chronic idiopathic myelofibrosis? A single-center study based on hematopoietic bone marrow histology

We reviewed a large series of patients with essential thrombocythemia diagnosed on the basis of the Polycythemia Vera Study Group criteria, and reclassified them by evaluating their major morphologic features and clinical course using the World Health Organization classification. The morphologic review of the bone marrow biopsies of 116 patients (44 males and 72 females; aged 19 - 83 years, median 55 years; median follow-up 121 months) led to 22 cases (19%) being classified as essential thrombocythemia (ET), 24 (21%) as chronic idiopathic myelofibrosis (CIMF)-0, 44 (37%) as CIMF-1, 13 (12%) as CIMF-2, 9 (8%) as latent phase polycythemia vera, and four (3%) as chronic myeloproliferative disorder, unclassifiable. There was a significant difference in the median age of the ET and fibrotic CIMF patients (54.7 +/- 13.55 vs. 59.13 +/- 15.05 years; P = 0.03). Histologic analysis showed that the simultaneous presence of loose clusters of large/giant megakaryocytes and nuclear hyperlobulation was significantly different between the ET and the prefibrotic CIMF (P<0.01) and fibrotic CIMF patients (P<0.01), and that the association of dense clusters of megakaryocytes with maturation defects and bulbous nuclei also distinguished the prefibrotic CIMF (P<0.05) and fibrotic CIMF patients (P<0.001) from those with ET. The association of cellularity, granulocytic proliferation and reticulin fibers was helpful in distinguishing prefibrotic from fibrotic CIMF (P<0.001).

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.

Chronic idiopathic myelofibrosis: clinicopathologic features, pathogenesis, and prognosis

CONTEXT

Chronic idiopathic myelofibrosis (CIMF) is a clonal myeloproliferative disease characterized by panmyelosis with intact maturation, progressive bone marrow fibrosis, and multiorgan extramedullary hematopoiesis.

OBJECTIVE

This review article aims to summarize the recent updates regarding the clinicopathologic features, molecular pathogenesis, cytogenetic abnormalities, diagnostic criteria, new diagnostic ancillary tests, and prognostic factors of CIMF.

DATA SOURCES

Important relevant articles indexed in PubMed/MEDLINE (National Library of Medicine) through the end of 2005 and referenced medical texts.

CONCLUSIONS

Because CIMF has a variety of clinical presentations, diagnosis may be challenging; the prefibrotic stage of CIMF has always been a challenging disease for pathologists to diagnose accurately. The recently proposed European Clinical and Pathological criteria can be helpful in the diagnosis of CIMF, especially in its prefibrotic stage. The enumeration of CD34-positive cells in the peripheral blood and the presence of circulating endothelial progenitor cells are the new important ancillary tests for the diagnosis of a small subset of patients with CIMF with atypical presentation. The recent discovery of the new mutation affecting the Janus tyrosine kinase 2 (JAK2V617F), more frequently observed in patients with polycythemia vera, is seen in approximately 35% to 57% of patients with CIMF. This mutation can serve as another diagnostic tool. Important factors affecting prognosis in CIMF are anemia, age of the patient, white blood cell count, degree of fibrosis, and number of blasts in the peripheral blood.

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.

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.

Grade of bone marrow fibrosis is associated with relevant hematological findings-a clinicopathological study on 865 patients with chronic idiopathic myelofibrosis

Controversy continues to exist regarding not only the exact definition and grading of myelofibrosis (MF), but also whether, and to what extent, this feature may be correlated with clinical findings. A retrospective study was performed involving 865 bone marrow (BM) biopsies together with the clinical records from patients with chronic idiopathic myelofibrosis (CIMF). Diagnosis was established according to the World Health Organization criteria, and assessment of MF followed a consensus scoring system that included four grades (MF-0 to MF-3). Histopathological and clinical evaluations were carried out in an independent fashion. Prefibrotic and early CIMF (MF-0/-1) were presented by 565 patients showing borderline to mild anemia and no or slight splenomegaly, but frequently, thrombocytosis exceeding 500x10(9)/l was shown. In 300 patients, manifest reticulin and collagen fibrosis (MF-2/-3) were characterized by marked anemia, gross splenomegaly, peripheral blasts, and normal to decreased platelet and leukocyte counts. The latter cohort was consistent with findings generally in keeping with MF with myeloid metaplasia. Regarding the stepwise evolution of disease, sequential BM examinations showed that in 103 patients, prefibrotic and early CIMF transformed into advanced stages accompanied by correspondingly developing clinical and histomorphological features. Survival analysis (univariate calculation) revealed a significantly more favorable prognosis in prefibrotic vs advanced stages of CIMF. On the other hand, higher classes of MF also exerted a higher clinical risk profile (Lille score). In conclusion, the dynamics of the disease process in CIMF are characterized by evolving MF in the BM and closely associated changes of relevant hematological findings.

Objective, planimetry-based assessment of megakaryocyte histological pictures in Philadelphia-chromosome-negative chronic myeloproliferative disorders: a perspective for a valuable adjunct diagnostic tool

Philadelphia-chromosome-negative chronic myeloproliferative disorders (Ph- CMPDs)--essential thrombocythemia (ET), chronic idiopathic myelofibrosis (CIMF), and polycythemia vera (PV)--may show clinical and morphological similarities, particularly at the early stages. The differential diagnosis of Ph- CMPDs is important due to their different treatment and prognosis. Cytological features of megakaryocytes are considered valuable in this differentiation. To establish an objective measure of megakaryocyte dysplasia in Ph- CMPDs, we performed computer-assisted morphometry of more than 4,000 cells from 20 cases of ET, 10 of CIMF, 10 of PV, and 10 controls. Megakaryocyte sets from three Ph- CMPDs differed significantly in respect to many planimetric parameters, but not a single shape or size parameter could have been used as a discriminative tool between the entities. However, the discriminant function analysis with the simultaneous assessment of 12 planimetric variables allowed for a proper classification of 20 of 20 ET, 10 of 10 PV, and 9 of 10 CIMF cases based solely on the morphometric features of megakaryocytes. Additionally, we identified certain new patterns of megakaryocytes specific for ET, PV, and CIMF, which, although not dominating in one Ph- CMPD, are unlikely to occur in two others. Objective measurements of megakaryocyte sizes and shapes may assist the diagnosis of Ph- CMPDs.

Increased incidence of monoclonal B-cell infiltrate in chronic myeloproliferative disorders

A total of 106 trephine biopsy specimens with clinical, laboratory and pathology findings corresponding to chronic myeloproliferative disorders (CMPD) were analyzed to reveal the nature of the lymphoid infiltrate in the bone marrow. Histological investigation in 31 chronic myeloid leukemia (CML), 29 CMPDs not otherwise specified (CMPD-NOS), 28 essential thrombocytosis (ET), 15 polycythemia vera (PV) and three chronic eosinophilic leukemia/hypereosinophilic syndrome (CEL/HES) exhibited in 32% various amounts of lymphocytic infiltrate of sparsely to moderately diffuse or nodular types in the bone marrow, but the reactive or coinciding lymphomatous nature could not be revealed by histology alone in the majority of cases. PCR analysis of the immunoglobulin heavy chain (IgH) gene rearrangement was successfully performed in 81 out of the 106 DNA specimens extracted from formol-paraffin blocks. Out of the 81 samples with good-quality DNA, 18 gave a single or double discrete amplification band(s), which was reproducible only in four specimens. Sequencing finally proved monoclonal B-cell population of both pre- and postfollicular origin in all four samples (5%), one CML and three CMPD-NOS. Detailed clinical and pathological investigations indicated overt B-cell malignant lymphoma with clonal relationship to the CMPD in two out of these four patients. We conclude that detailed molecular analysis of IgH gene rearrangement in bone marrow samples of CMPD patients is needed to identify the true monoclonal B-cell infiltration, which-even without overt malignant lymphoma-may occur in this group of disorders. Modern Pathology (2004) 17, 1521-1530, advance online publication, 16 July 2004; doi:10.1038/modpathol.3800225.

Dynamics of fibrosis in chronic idiopathic (primary) myelofibrosis during therapy: a follow-up study on 309 patients

Controversial issues in chronic idiopathic myelofibrosis (IMP) are amongst others the evolution of the disease process and the influence of therapy on the dynamics of fibrosis. For this reason, a multicenter observational study was performed on 309 patients with IMF that had a long follow-up including 822 bone marrow biopsies at a median interval of 32 months. In addition to a control group (156 patients) with symptomatic treatment, monotherapy consisted of busulfan (30 patients), hydroxyurea (52 patients), interferon (26 patients) and various combinations (48 patients). Density and quality (reticulin/collagen) of fibers was determined by a semiquantitative scoring system. Independent of therapeutic regimens at the time of the last bone marrow biopsy 67% of the patients with grades 0-2 fibrosis revealed a progression, 42% stable state and 6% regression of myelofibrosis. Because of significant differences concerning frequencies of biopsies and endpoints of examinations, individual changes in the grades of fibrosis were evaluated with regard to treatment applied at standardized intervals of 20 months. According to this calculation no relevant differences in the dynamics of myelofibrosis (progression, stable state) was detectable in the control group compared to the other therapeutic modalities. The few patients with a regression of myelofibrosis usually presented with severe hypoplasia compatible with a myelo-ablative effect by aggressive chemotherapy. In conclusion, persuasive evidence has been produced that myelofibrosis in IMF is characterized by a stepwise progression and that this process is not significantly influenced by current treatment strategies.

Philadelphia chromosome and/or bcr-abl mRNA-positive primary thrombocytosis: morphometric evidence for the transition from essential thrombocythaemia to chronic myeloid leukaemia type of myeloproliferation

AIMS

The incidence, bone marrow morphology and genetic features of bcr+ essential thrombocythaemia were investigated.

METHODS AND RESULTS

Sixty-four consecutive patients meeting the criteria of essential thrombocythaemia have been investigated for bcr-abl rearrangement and chimera mRNA expression. Reverse transcriptase-polymerase chain reaction indicated bcr-abl expression in six patients, in two of whom large fraction of the blood and bone marrow cells proved to be positive for Philadelphia chromosome (Ph) by fluorescent in-situ hybridization (FISH) and conventional cytogenetic analysis. In the remaining four patients FISH analysis could not detect Ph+ cells among the blood cells, but in one of these four patients conventional cytogenetic analysis indicated a very small fraction (2%) of Ph+ mitoses in the bone marrow (bcr+ essential thrombocythaemia patients). In three of these four patients, X-chromosome-linked clonality assay showed that the disease is of uncommitted stem cell origin. During an average of 57 month long follow-up no transformation to chronic myeloid leukaemia type of disease or acceleration/blastic crisis could be observed in the four bcr+ essential thrombocythaemia patients. They did not differ significantly from typical essential thrombocythaemia patients in quantitative indices of bone marrow cellularity or the size of megakaryocytes. In these two parameters as well as in the total nucleolus organizer region area per nucleus, however, significant differences could be detected between these four as well as typical chronic myeloid leukaemia patients. Statistical analysis of the morphometric data obtained from all six Ph+ and bcr+ essential thrombocythaemia patients combined indicated a shift of the bone marrow morphology towards the chronic myeloid leukaemia type of myeloproliferation.

CONCLUSIONS

These investigations indicate that bcr+ essential thrombocythaemia is infrequent among essential thrombocythaemia patients, and this condition resembles essential thrombocythaemia more than chronic myeloid leukaemia. Various expansions of the Ph+ clone appear to lead to either essential thrombocythaemia or, rather, chronic myeloid leukaemia type of myeloproliferation; however, data in the present study do not indicate that bcr+ essential thrombocythaemia would be a form fruste variant of chronic myeloid leukaemia.

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.

Bone marrow features improve prognostic efficiency in multivariate risk classification of chronic-phase Ph(1+) chronic myelogenous leukemia: a multicenter trial

PURPOSE

Multivariate risk classifications for chronic (stable)-phase Ph(1+) chronic myelogenous leukemia (CML) are generally focused on hematologic variables, and the putative prognostic property of bone morphology has been neglected or even contested so far.

PATIENTS AND METHODS

A total of 510 consecutively recruited patients in first chronic phase Ph(1+) CML and pretreatment bone marrow biopsy specimens were entered onto this multicenter observational trial to evaluate the effect of bone marrow histopathology. According to generally accepted criteria, patients with any signs of accelerated disease were excluded. Treatment modalities included administration of interferon alfa-2b (IFN) and chemotherapy with hydroxyurea (HU) or busulfan. Immunohistochemical and morphometric techniques were applied to identify marrow cells and to quantify fiber density. Patients were separated into learning and validation samples, and classification and regression tree (CART) analysis was performed to establish a prognostic decision tree.

RESULTS

CART analysis of the validation sample (123 patients with HU therapy) revealed the amount of erythroid precursors in the bone marrow, myelofibrosis, and splenomegaly as the most important prognostic features. Three risk profiles with significantly different survival patterns were established, with median survival times ranging from 33 to 108 months (two-sided log-rank test, P =.0001). The new score was confirmed by application to the learning sample with IFN therapy (two-sided log-rank test, P =.0002). Furthermore, risk status defined by the new score was significantly correlated with the occurrence of blast transformation.

CONCLUSION

Our data strongly implicate that prognostic classification of chronic-phase Ph(1+) CML can be significantly improved by the inclusion of morphologic parameters. The variables of the presented scoring system may be easily assessed by routinely processed aspirates and bone marrow trephines.

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.

Prognostic impact of bone marrow erythropoietic precursor cells and myelofibrosis at diagnosis of Ph1+ chronic myelogenous leukaemia--a multicentre study on 495 patients

A multicentre clinicopathological study was performed on 495 patients with chronic-phase Ph1+ chronic myelogenous leukaemia (CML) to determine bone marrow characteristics that exert a significant impact on survival under standard treatment regimens. Immunohistochemical and morphometric techniques were applied to identify nucleated erythroid precursor cells in the bone marrow and to quantify argyrophilic fibre density. Application of the Sokal index and another recently proposed CML score failed to distinguish three clearly defined risk groups. A borderline increase in fibre content (i.e. doubling of the normal density) and a relevant reduction of medullary erythropoiesis proved to be important predictors for survival, even in low-risk classified patients, according to both clinical scores. With regard to optimal treatment strategies, patients with manifest myelofibrosis showed no significant difference in survival rates under interferon or hydroxyurea treatment. Multivariate analysis confirmed the prognostic value of histological features. A risk model based on three variables (fibre density, erythropoietic precursors and spleen size) was constructed that enabled a distinct discrimination of risk profiles. In conclusion, the presented data provide compelling evidence that bone marrow features at diagnosis exert a significant impact on prognosis in CML. In this context, the generally clinical-based multivariate risk classification can be improved by consideration of morphological variables that are acting independently of treatment modalities.

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.

Relevance and dynamics of myelofibrosis regarding hematopoietic reconstitution after allogeneic bone marrow transplantation in chronic myelogenous leukemia--a single center experience on 160 patients

A retrospective single center study was performed on 516 trephine biopsies derived from 160 patients with stable phase Ph+-CML and allogeneic BMT. Following morphometric quantification of reticulin-collagen fibers we tried to elucidate (1) the dynamics of bone marrow fibrosis in the post-transplant period; and (2) the influence of manifest myelofibrosis on relevant engraftment parameters. An evaluation of fiber density at standardized endpoints after BMT was carried out on a selected cohort of 124 patients (399 biopsy specimens). A manifest myelofibrosis (more than a three-fold increase compared to the normal fiber content) before BMT was found in 26% of our patients. Concentrating on bone marrow areas with reconstituting hematopoiesis, several findings emerged. Pretransplant myelofibrosis was associated with an initial regression following BMT, but insidiously recurred in the areas of regenerating hematopoiesis or developed in a few patients without increased pregraft fibers during the post-transplant period (mean observation time more than 4 months). Severe acute GVHD (grades III and IV) was significantly correlated with a greater amount of reticulin fibers in the early post-transplant period (9 to 30 days after BMT). Regarding engraftment parameters, a significant delay was detectable in the time to achieve transfusion independence for the patients with manifest myelofibrosis compared to those without pre-transplant fiber increase.

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.

Diagnosis and treatment of polycythemia vera and possible future study designs of the PVSG

The present study describes clinicopathological criteria to distinguish the 5 sequential stages proposed by Wasserman et al in the natural history of newly diagnosed PV patients. The European Working Group on MPD (EWG.MPD) extended and modified the PVSG diagnostic criteria of PV by including bone marrow histopathology. From the results of prospective randomized studies in PV it became evident that new clinical trials in previously untreated PV patients should focus on comparing interferon-alpha, a non-leukemogenic approach, versus a potential leukemogenic myelosuppressive treatment modality. Hydroxyurea appears to be the least leukemogenic myelosuppressive agent in long-term prospective clinical PV-studies extending observation periods of more than 10 years. The rational for using IFN-alpha as a first-line treatment option in newly diagnosed PV-patient include its effectiveness to abate constitutional symptoms and to induce a complete remission thereby avoiding phlebotomy, iron deficiency, and macrocytosis associated with hydroxyurea. Moreover IFN-alpha may prevent or delay the development of postpolycythemic myelofibrosis if used early in the course of the disease. Clinicians will be reluctant to postpone the use of hydroxyurea in early stage PV as long as a conservative approach using phlebotomy aiming at a hematocrit below 0.45, plus low-dose aspirin for the control platelet function or anagrelide for the control platelet number is used to keep the patient healthy. Low-dose aspirin will prevent the microvascular thrombotic complications of thrombocythemia associated with PV in remission after phlebotomy, but lacks myelosuppressive activity. Control of megakaryocyte maturation and reduction of platelet production to normal (<400 x 10(9)/l) by relatively low doses of anagrelide will predict a significant reduction of vascular complications in the early stages of PV, may prevent progression to myelofibrosis during follow-up of PV and very probable will postpone the use of hydroxyurea treatment for controlling the platelet count in PV. Large scale randomized clinical trials in PV are proposed, which should aim not only for clinical and hematological response, safety, efficacy, but should also assess toxicity, the need for phlebotomy and whether the development of progressive disease such as splenomegaly, pruritus, myelofibrotic myeloid metaplasia, spent phase, myelodysplasia and acute leukemia can be delayed or prevented by IFN-alpha as compared to a conservative approach of phlebotomy plus low-dose aspirin or anagrelide followed by hydroxyurea when signs of myeloproliferative activity became evident.

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.

Myelofibrosis with myeloid metaplasia: diagnostic definition and prognostic classification for clinical studies and treatment guidelines

PURPOSE

Myelofibrosis with myeloid metaplasia (MMM) is a chronic myeloproliferative disorder characterized by bone marrow fibrosis and extramedullary hematopoiesis. Recent studies provide definite diagnostic criteria and prognostic classifications of the disease, and allogeneic stem-cell transplantation (SCT) now offers a chance of curing the disease. In order to put diagnostic criteria and prognostic classifications of the disease into the perspective of developing guidelines for treatment strategies, all studies published in the English literature over the last 30 years were reviewed.

MATERIALS AND METHODS

Studies were identified through a MEDLINE search (1966 to present) and from the bibliographies of relevant articles.

RESULTS

The Italian Consensus Conference on diagnostic criteria is a structured enterprise aimed at formulating a definition of MMM that will be used for enrolling patients onto clinical studies. It relies on the obligatory presence of myelofibrosis and on the exclusion of the BCR-ABL rearrangement or Philadelphia chromosome, in association with combinations of traditional features. Prognostic scores allow us to identify classes of patients on the basis of hemoglobin, age, WBC count, and chromosomal abnormalities. Several nonrandomized studies have indicated that allogeneic SCT for patients under the age of 55 is effective in prolonging survival in more than 50% of cases and in possibly curing the disease. Patients with the most severe prognosis are candidates.

CONCLUSION

"Consensus" methodology offers a definition of MMM useful for conducting and reporting clinical studies. A detailed knowledge of prognostic factors can help to delineate guidelines for addressing patients with allogeneic SCT.

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.

The Italian Consensus Conference on Diagnostic Criteria for Myelofibrosis with Myeloid Metaplasia

The purpose of this work was to develop a definition of myelofibrosis with myeloid metaplasia (MMM) using diagnostic criteria that would remain valid within the set of patients with chronic myeloproliferative disorders or myelodysplastic syndromes. A list of 12 names for the disease and 37 diagnostic criteria were proposed to a Consensus Panel of 12 Italian experts who ranked them in order so as to identify a core set of criteria. The Panel was then asked to score the diagnosis of 46 patient profiles as appropriate or not appropriate for MMM. Using the experts' consensus as the gold standard, the performance of 90 possible definitions of the disease obtained through the core set was evaluated. 'Myelofibrosis with myeloid metaplasia' ranked as the preferred name of the disease. Necessary criteria consisted of 'diffuse bone marrow fibrosis' and 'absence of Philadelphia chromosome or BCR-ABL rearrangement in peripheral blood cells'. The six optional criteria in the core set consisted of: splenomegaly of any grade; anisopoikilocytosis with tear-drop erythrocytes; the presence of circulating immature myeloid cells; the presence of circulating erythroblasts: the presence of clusters of megakaryoblasts and anomalous megakaryocytes in bone marrow sections; myeloid metaplasia. The definition of the disease with the highest final score was as follows: necessary criteria plus any other two criteria when splenomegaly is present or any four when splenomegaly is absent. The use of this definition will help to standardize the conduct and reporting of clinical studies and should help practitioners in clinical practice.

The histopathology of chronic myeloproliferative diseases

This chapter discusses the histopathology of five groups of chronic myeloproliferative diseases: chronic myeloid leukaemia, polycythaemia vera, essential thrombocythaemia, chronic idiopathic myelofibrosis and unclassifiable myeloproliferation. Histological staging of the four haematologically defined diseases is performed by grading the three most prominent variables: megakaryocytes, fibres and blasts. Histological outcome is correlated to the staging of diagnostic bone marrow biopsies; megakaryocytic involvement is correlated with the risk of myelofibrosis. An excess of blasts is related to the risk of leukaemic transformation. The progression of myelofibrosis depends on the grade of fibre increase at diagnosis. These three statements are highly significant and valid for all types of chronic myeloproliferative disorders. The results of cytogenetics are discussed in relation to the histological classification for these patient groups. Changes in bone marrow histology following myelosuppressive therapy is presented. Prospective studies under standardized protocol therapy are recommended, so that the long-term effects of therapy can be assessed.

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.

Value of fluorescence in situ hybridization for detecting the bcr/abl gene fusion in interphase cells of routine bone marrow specimens

Fluorescence in situ hybridization (FISH) is a new technique that allows demonstrating of the bcr/abl gene fusion in bone marrow cells of patients with Philadelphia translocation (Ph)-positive chronic myeloid leukemia (CML). In this study, bone marrow samples of 150 patients were investigated routinely by interphase FISH, cytogenetics, and bone marrow histopathology. In 20 patients with reactive hyperplasia of the granulopoiesis and normal karyotypes, FISH revealed nonspecific bcr/abl fusion signals at a mean frequency of 2.7% of the cells examined. The cutoff level for specific fusion signals was set at three times the standard deviation (9.0%). None of the 29 cytogenetically Ph-negative patients with myeloproliferative disease other than CML had fusion signals exceeding 9%. The mean frequency of specific fusion signals in nontreated patients with CML (n = 59) was 92.7%, and 49.3% in patients with CML who received therapy (n = 42). For diagnosing Ph-positive CML, interphase FISH has been faster, more reliable, and more sensitive than cytogenetics, which was successful in 54 of 59 patients investigated at first diagnosis but only in 27 of 42 patients receiving therapy, and it failed to detect Ph-positive cells in three patients with CML. However, small percentages of less than 9.0% of cells with bcr/abl fusion signals were below the threshold of interphase FISH, thereby limiting its use for detecting minimal residual disease.

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.

Megakaryocytes and platelets in myeloproliferative disorders

Increased megakaryocyte (MK) proliferation in bone marrow is a feature common to the three Ph-negative myeloproliferative disorders (MPDs), i.e. essential thrombocythaemia (ET), polycythaemia vera (PV), and myelofibrosis with splenic myeloid metaplasia (MMM), and to chronic myelocytic leukaemia (CML). Enlarged MKs with multilobulated nuclei and cell clustering in close proximity are the hallmark of all the Ph negative MPDs. Clonality of haematopoietic cells, based on X chromosome inactivation, can now be studied in a majority of female patients in all nucleated cell fractions as well as in platelets. Cytofluorometric studies have demonstrated a shift towards higher ploidy classes in PV and ET MKs which may be useful in discriminating between both primary and reactive thrombocytosis and CML patients which show a significant shift to lower MK ploidy values. The role of MK proliferation on the evolution of myelofibrosis common to MPDs has been firmly established. Implication of platelet-derived growth factor (PDGF) in myelofibrosis has already been demonstrated. More recently transforming growth factor beta (TGF beta) synthesized and secreted by MK has been implicated in fibroblasts stimulation. A significant increase in circulating colony-forming units of MKs (CFU-MK) has been repeatedly observed in MPDs as well as a spontaneous MK colony formation in a majority of ET patients. Hypersensitivity to thrombopoietin (TPO) in relation to a functional defect of the TPO-MPL pathway may play a major role in spontaneous MK growth. There is no currently available test of platelet functions able to predict the risk of occurrence of thrombotic or haemorrhagic complications in MPD patients. However, the role of platelet activation in the pathogenesis of ischaemic erythromelalgia has been established and a correlation between presenting haemorrhagic manifestations and platelet counts in excess of 1000 x 10(9)/l has been found.

Relationship between the type of BCR-ABL rearrangement and bone marrow histopathological features in chronic myeloid leukemia

The aim of the present study was to characterize the type of BCR-ABL transcript and to correlate the molecular feature with bone marrow histology. For this purpose, we analysed the BCR-ABL rearrangement in 26 patients with chronic myeloid leukemia (CML) in the chronic phase by RT-PCR, and we also classified the bone marrow histology according to the predominance of granulocylic (GRAN) or granulocytic and megakaryocytic (GRAM/MEG) proliferation, after analysis of two independent observers. We did not find any significant difference in survival of patients presenting b2-a2 and b3-a2 transcripts or GRAN and GRAN/MEG bone marrow types, nor did we find any significant correlation of the type of BCR-ABL transcript with the bone marrow histological subgroups GRAN and GRAN-MEG (Fisher's test = 0.31). Thus, we conclude that the presence of exon b3 is not correlated to bone marrow histology in CML.

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.