The incidence of myelofibrosis in essential thrombocythaemia, polycythaemia vera and chronic idiopathic myelofibrosis: a retrospective evaluation of sequential bone marrow biopsies

Bone marrow morphological features and therapy in patients with Philadelphia-negative neoplasms

Introduction Chronic myeloproliferative neoplasm (MPNs) are clonal malignant bone marrow (BM) diseases, arising from a hematopoietic stem cell. All therapies for these neoplasms have peculiar effects on the bone marrow, but little evidence has been described in the literature.Areas covered This review examines BM morphological changes following the main treatments in Philadelphia-negative MPNs. Hydroxyurea can reduce the cellularity of the erythroid and megakaryocyte lineages but has minimal impact on fibrotic evolution. There is general agreement on its dysplastic effects, with a high incidence of acute myeloid leukemia and myelodysplastic syndrome. Interferon treatment can reduce or normalize BM cellularity, improve erythropoiesis, and reduce the number and atypicality of megakaryocytes. Most data describe reduction or complete resolution of marrow fibrosis; dysplastic effects are not reported. Anagrelide may induce an increase in the number of BM megakaryocytes, especially immature megakaryocytes or precursors, and a worsening of marrow fibrosis or increased transformation of essential thrombocythemia into myelofibrosis. Ruxolitinib can improve or stabilize BM fibrosis and reduces the frequency and dense clustering of megakaryocytes.Expert opinion Since previous therapy can modify BM features, it is essential to obtain information on previous or current therapies and to collect complete clinical information.

Synoptic Diagnostics of Myeloproliferative Neoplasms: Morphology and Molecular Genetics

Simple Summary

The diagnosis of myeloproliferative neoplasms requires assessment of a combination of clinical, morphological, immunophenotypic and genetic features, and this integrated, multimodal approach forms the basis for precise classification. Evaluation includes cell counts and morphology in the peripheral blood, bone marrow aspiration and trephine biopsy, and may encompass flow cytometry for specific questions. Diagnosis nowadays is completed by targeted molecular analysis for the detection of recurrent driver and, optionally, disease-modifying mutations. According to the current World Health Organization classification, all myeloproliferative disorders require assessment of molecular features to support the diagnosis or confirm a molecularly defined entity. This requires a structured molecular analysis workflow tailored for a rapid and cost-effective diagnosis. The review focuses on the morphological and molecular features of Ph-negative myeloproliferative neoplasms and their differential diagnoses, addresses open questions of classification, and emphasizes the enduring role of histopathological assessment in the molecular era.

Abstract

The diagnosis of a myeloid neoplasm relies on a combination of clinical, morphological, immunophenotypic and genetic features, and an integrated, multimodality approach is needed for precise classification. The basic diagnostics of myeloid neoplasms still rely on cell counts and morphology of peripheral blood and bone marrow aspirate, flow cytometry, cytogenetics and bone marrow trephine biopsy, but particularly in the setting of Ph− myeloproliferative neoplasms (MPN), the trephine biopsy has a crucial role. Nowadays, molecular studies are of great importance in confirming or refining a diagnosis and providing prognostic information. All myeloid neoplasms of chronic evolution included in this review, nowadays feature the presence or absence of specific genetic markers in their diagnostic criteria according to the current WHO classification, underlining the importance of molecular studies. Crucial differential diagnoses of Ph− MPN are the category of myeloid/lymphoid neoplasms with eosinophilia and gene rearrangement of PDGFRA, PDGFRB or FGFR1, or with PCM1-JAK2, and myelodysplastic/myeloproliferative neoplasms (MDS/MPN). This review focuses on morphological, immunophenotypical and molecular features of BCR-ABL1-negative MPN and their differential diagnoses. Furthermore, areas of difficulties and open questions in their classification are addressed, and the persistent role of morphology in the area of molecular medicine is discussed.

New Perspectives on Polycythemia Vera: From Diagnosis to Therapy

Polycythemia vera (PV) is mainly characterized by elevated blood cell counts, thrombotic as well as hemorrhagic predisposition, a variety of symptoms, and cumulative risks of fibrotic progression and/or leukemic evolution over time. Major changes to its diagnostic criteria were made in the 2016 revision of the World Health Organization (WHO) classification, with both hemoglobin and hematocrit diagnostic thresholds lowered to 16.5 g/dL and 49% for men, and 16 g/dL and 48% for women, respectively. The main reason leading to these changes was represented by the recognition of a new entity, namely the so-called “masked PV”, as individuals suffering from this condition have a worse outcome, possibly owing to missed or delayed diagnoses and lower intensity of treatment. Thrombotic risk stratification is of crucial importance to evaluate patients’ prognosis at diagnosis. Currently, patients are stratified into a low-risk group, in the case of younger age (<60 years) and no previous thromboses, and a high-risk group, in the case of patients older than 60 years and/or with a previous thrombotic complication. Furthermore, even though they have not yet been formally included in a scoring system, generic cardiovascular risk factors, particularly hypertension, smoking, and leukocytosis, contribute to the thrombotic overall risk. In the absence of agents proven to modify its natural history and prevent progression, PV management has primarily been focused on minimizing the thrombotic risk, representing the main cause of morbidity and mortality. When cytoreduction is necessary, conventional therapies include hydroxyurea as a first-line treatment and ruxolitinib and interferon in resistant/intolerant cases. Each therapy, however, is burdened by specific drawbacks, underlying the need for improved strategies. Currently, the therapeutic landscape for PV is still expanding, and includes several molecules that are under investigation, like long-acting pegylated interferon alpha-2b, histone deacetylase inhibitors, and murine double minute 2 (MDM2) inhibitors.

3023 Mayo Clinic Patients With Myeloproliferative Neoplasms: Risk-Stratified Comparison of Survival and Outcomes Data Among Disease Subgroups

OBJECTIVE

To document the Mayo Clinic decades-long experience with myeloproliferative neoplasms (MPNs) and provide mature risk-stratified survival data and disease complication estimates.

PATIENTS AND METHODS

All Mayo Clinic patients with World Health Organization-defined MPNs constituted the core study group and included those with polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF).

RESULTS

A total of 3023 consecutive patients (median age, 62 years; range, 18-96 years) were considered: 665 PV, 1076 ET, and 1282 PMF. From October 27, 1967, through December 29, 2017, 1631 deaths (54%), 183 leukemic transformations (6%), 244 fibrotic progressions (14%), and 516 thrombotic events (17%) were recorded. Median overall survival (OS) was 18 years for ET, 15 years for PV, and 4.4 years for PMF (P<.05 for all intergroup comparisons). Inferior survival was documented in patients with ET diagnosed more recently (post-1990) (P<.001), whereas survival data were time independent in PV and PMF. After conventional risk stratification, OS in low-risk ET and low-risk PV were superimposed (P=.89) but each differed significantly from that of age- and sex-matched controls (P<.001). Leukemia-free survival was similar for ET and PV (P=.22) and significantly worse with PMF (P<.001). Compared with ET, PV was associated with higher risk of fibrotic progression (P<.001). Thrombosis risk after diagnosis was highest in PV and lowest in PMF (P=.002 for PV vs ET; P=.56 for ET vs PMF; and P=.001 for PV vs PMF).

CONCLUSION

This study provides the most mature survival and outcomes data in MPNs and highlights MPN subgroup risk categorization as key in appraising disease natural history. The OS was only marginally better in ET compared with PV, and PV displayed a higher risk of thrombosis and fibrotic progression.

Prognostication in Philadelphia Chromosome Negative Myeloproliferative Neoplasms: a Review of the Recent Literature

PURPOSE OF REVIEW

The prognosis for patients with Philadelphia chromosome (Ph)-negative myeloproliferative neoplasms (MPNs) is highly variable. All Ph-negative MPNs carry an increased risk for thrombotic complications, bleeding, and leukemic transformation. Several clinical, biological, and molecular prognostic factors have been identified in recent years, which provide important information in guiding management of patients with Ph-negative MPNs. In this review, we critically evaluate the recent published literature and discuss important new developments in clinical and molecular factors that impact survival, disease transformation, and thrombosis in patients with polycythemia vera, essential thrombocythemia, and primary myelofibrosis.

RECENT FINDINGS

Recent studies have identified several clinical factors and non-driver mutations to have prognostic impact on Ph-negative MPNs independent of conventional risk stratification and prognostic models. In polycythemia vera (PV), leukocytosis, abnormal karyotype, phlebotomy requirement on hydroxyurea, increased bone marrow fibrosis, and mutations in ASXL1, SRSF2, and IDH2 were identified as additional adverse prognostic factors. In essential thrombocythemia (ET), JAK2 V617F mutation, splenomegaly, and mutations in SH2B3, SF3B1, U2AF1, TP53, IDH2, and EZH2 were found to be additional negative prognostic factors. Bone marrow fibrosis and mutations in ASXL1, SRSF2, EZH2, and IDH1/2 have been found to be additional prognostic factors in primary myelofibrosis (PMF). CALR mutations appear to be a favorable prognostic factor in PMF, which has not been clearly demonstrated in ET. The prognosis for patients with PV, ET, and PMF is dependent upon the presence or absence of several clinical, biological, and molecular risk factors. The significance of additional risk factors identified in these recent studies will need further validation in prospective studies to determine how they may be best utilized in the management of these disorders.

Extramedullary haematopoiesis presenting with cardiac tamponade in a patient with polycythaemia vera

A 71-year-old man with a history of polycythaemia vera, diagnosed 4 years ago, presented to the emergency room with shortness of breath. A bedside echocardiogram revealed a large pericardial effusion with features concerning for pericardial tamponade. A left anterior thoracotomy and a pericardial window were emergently performed in the operating room and relieved the patient's symptoms. Histology evaluation of the pericardial fragments and pericardial fluid revealed the presence of trilineage haematopoietic elements without any increase in the blasts. A bone marrow core biopsy revealed an increase in reticulin fibre and increase in the number of blasts of 5%-10%, whereas peripheral blood testing was positive for JAK2 V617F mutation. This case report reviews the literature for cases of extramedullary haematopoiesis associated with myeloproliferative neoplasms.

Comparison of JAK2V617F -positive essential thrombocythaemia and early primary myelofibrosis: The impact of mutation burden and histology

An accurate histological diagnosis may distinguish essential thrombocythaemia (ET) from early primary myelofibrosis (early-PMF), which is associated with worse outcome. Outcome of ET is also negatively affected by the presence of the JAK2^V617F mutation. To investigate the impact of JAK2^V617F mutation burden and histology on outcome, we collected 475 WHO-diagnosed ET (69.2%) or early-PMF JAK2^V617F -positive patients followed in 4 Italian haematology centers. JAK2^V617F allele burden was ≤50% in 90% and 87% of ET and early-PMF patients, respectively (P = .34). During follow-up, 32 (9.7%) ET and 18 (12.3%) early-PMF patients experienced 59 thrombotic events, and 27 patients (5.6%) and 6 (1.2%) patients evolved to myelofibrosis and acute leukemia, respectively. At last contact, 28 (5.8%) patients had died. In early-PMF compared to ET, the 10-year mortality rates (6.7% and 4.3%, P = .73), leukemic transformation rates (1.4% and 1.2%, P = .45), and thrombosis rates (16.7% and 12.2%, P = .12) were comparable. Only progression to overt myelofibrosis at 10 years was significantly worse (11.4% and 1.5%, P = .004). In multivariate analysis, a higher (>50%) JAK2^V617F burden was significantly correlated with fibrotic progression and histology. Considering JAK2^V617F -positive disease, a higher (>50%) JAK2^V617F burden and histological classification are independent prognostic risk factors for disease progression. These findings reinforce the need for standardized detection of this mutation.

Prognostic impact of bone marrow fibrosis in polycythemia vera: validation of the IWG-MRT study and additional observations

In 2012, the International Working Group for Myeloproliferative Neoplasms (MPN) Research and Treatment (IWG-MRT) reported an associations between mild bone marrow (BM) fibrosis (⩾grade 1) in polycythemia vera (PV) and a lower incidence of thrombosis during the clinical course and a higher risk of fibrotic progression. The objective in the current study of 262 patients with PV was to validate these observations and also identify other risk factors for myelofibrosis-free survival (MFFS). About 127 (48%) patients displayed ⩾grade 1 reticulin fibrosis at the time of diagnosis; presenting clinical and laboratory features were not significantly different between patients with or without BM fibrosis. In univariate analysis, BM fibrosis had no significant impact on overall, leukemia-free or thrombosis-free survival, whereas a significant association was noted for MFFS (P=0.009, hazard ratio 2.9; 95% confidence interval 1.32–6.78); other risk factors for MFFS included leukocytosis ⩾15 × 10⁹/l, presence of palpable splenomegaly and abnormal karyotype. During multivariable analysis, leukocytosis ⩾15 × 10⁹/l, palpable splenomegaly and ⩾grade 1 BM reticulin fibrosis remained significant. The current study validates the previously observed association between ⩾grade 1 BM reticulin fibrosis in PV and subsequent fibrotic progression, and identifies leukocytosis and palpable splenomegaly as additional risk factors for fibrotic progression; additional studies are required to clarify the impact of BM fibrosis on thrombosis and that of abnormal karyotype on MFFS.

The 2016 revision of WHO classification of myeloproliferative neoplasms: Clinical and molecular advances

Clinical evidence supports the need of changing the diagnostic criteria of the 2008 updated WHO classification for polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF). In JAK2-mutated patients who show characteristic bone marrow (BM) morphology, clinical studies demonstrated that a hemoglobin level of 16.5g/dL in men and 16.0g/dl for women or a hematocrit value of 49% in men and 48% in women are the optimal cut off levels for distinguishing JAK2-mutated ET from "masked/prodromal" PV. Therefore BM morphology was upgraded to a major diagnostic criterion. Regarding ET the key issue was to improve standardization of prominent BM features enhancing differentiation between "true" ET and prefibrotic/early primary myelofibrosis (prePMF). These two entities have shown a different epidemiology and clinical outcomes. Concerning prePMF a more explicit clinical characterization of minor criteria is mandated for an improved distinction from ET and overt PMF and accurate diagnosis and outcome prediction.

Myeloproliferative neoplasms: Morphology and clinical practice

In myeloproliferative neoplasms (MPNs), controversy persists regarding the usefulness and reproducibility of bone marrow (BM) features. Disagreements concerning the WHO classification are mainly focused on the discrimination between essential thrombocythemia (ET) and prefibrotic/early primary myelofibrosis (prePMF) and prodromal polycythemia vera (PV). Criticism mostly refers to lack of standardization of distinctive BM features precluding correct morphological pattern recognition. The distinction between WHO-defined ET and prePMF is not trivial because outcome is significantly worse in prePMF. Morphology was generally considered to be non-specific for the diagnosis of PV. Recent studies have revealed under-diagnosis of morphologically and biologically consistent PV.

Incidence and patient survival of myeloproliferative neoplasms and myelodysplastic/myeloproliferative neoplasms in the United States, 2001-12

Descriptive epidemiological information on myeloproliferative neoplasms (MPNs) and myelodysplastic (MDS)/MPNs is largely derived from single institution and European population-based studies. Data obtained following adoption of the World Health Organization classification of haematopoietic neoplasms and JAK2 V617F mutation testing are sparse. Using population-based data, we comprehensively assessed subtype-specific MPN and MDS/MPN incidence rates (IRs), IR ratios (IRRs) and relative survival (RS) in the United States (2001-12). IRs were highest for polycythaemia vera (PV) (IR = 10·9) and essential thrombocythaemia (ET) (IR = 9·6). Except for ET and mastocytosis, overall IRs were significantly higher among males (IRRs = 1·4-2·3). All evaluable MPNs were associated with lower IRs among Hispanic whites than non-Hispanic whites (NHWs), with the exception of BCR-ABL1-positive chronic myeloid leukaemia (CML), chronic eosinophilic leukaemia (CEL) and juvenile myelomonocytic leukaemia. Except for CEL, Asians/Pacific Islanders had significantly lower MPN IRs than NHWs. ET, MPN-unclassifiable and CEL IRs were 18%, 19% and 60% higher, respectively, among blacks than NHWs. Five-year RS was more favourable for younger (<60 years) than older individuals and for women compared with men, except for PV at older ages. RS was highest (>90%) for younger PV and ET patients and lowest (<20%) for older chronic myelomonocytic leukaemia and atypical BCR-ABL1-negative CML patients. Varying MPN and MDS/MPN incidence patterns by subtype support distinct aetiologies and/or susceptible populations. Decreased survival rates as compared to that expected in the general population were associated with every MPN subtype, highlighting the need for new treatments, particularly among older individuals.

Rationale for revision and proposed changes of the WHO diagnostic criteria for polycythemia vera, essential thrombocythemia and primary myelofibrosis

The 2001/2008 World Health Organization (WHO)-based diagnostic criteria for polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF) were recently revised to accomodate new information on disease-specific mutations and underscore distinguishing morphologic features. In this context, it seems to be reasonable to compare first major diagnostic criteria of the former WHO classifications for myeloproliferative neoplasm (MPN) and then to focus on details that have been discussed and will be proposed for the upcoming revision of diagnostic guidelines. In PV, a characteristic bone marrow (BM) morphology was added as one of three major diagnostic criteria, which allowed lowering of the hemoglobin/hematocrit threshold for diagnosis, which is another major criterion, to 16.5 g/dl/49% in men and 16 g/dl/48% in women. The presence of a JAK2 mutation remains the third major diagnostic criterion in PV. Subnormal serum erythropoietin level is now the only minor criterion in PV and is used to capture JAK2-unmutated cases. In ET and PMF, mutations that are considered to confirm clonality and specific diagnosis now include CALR, in addition to JAK2 and MPL. Also in the 2015 discussed revision, overtly fibrotic PMF is clearly distinguished from early/prefibrotic PMF and each PMF variant now includes a separate list of diagnostic criteria. The main rationale for these changes was to enhance the distinction between so-called masked PV and JAK2-mutated ET and between ET and prefibrotic early PMF. The proposed changes also underscore the complementary role, as well as limitations of mutation analysis in morphologic diagnosis. On the other hand, discovery of new biological markers may probably be expected in the future to enhance discrimination of the different MPN subtypes in accordance with the histological BM patterns and corresponding clinical features.

Acute Myeloid Leukemia and Other Types of Disease Progression in Myeloproliferative Neoplasms

OBJECTIVES

This session of the Society for Hematopathology/European Association for Haematopathology workshop focused on disease progression in myeloproliferative neoplasms (MPNs).

METHODS

The session included typical and unusual presentations of chronic myelogenous leukemia (CML), BCR-ABL1 positive; Philadelphia chromosome-negative (Ph-neg) MPNs; and mastocytosis.

RESULTS

Cases of CML illustrated various manifestations of progression, with emphasis on criteria defining stages of the disease. Issues were discussed related to the patterns of recurrence in patients receiving tyrosine kinase inhibitor therapy, including leukemic transformation occurring in a Ph-neg clone. Ph-neg MPN cases highlighted diagnostic approaches used to establish accelerated and blast phases, including cases with significant myelofibrosis and when an adequate bone marrow aspirate smear is not available. The session also included rare cases of aggressive mastocytosis.

CONCLUSIONS

There was agreement that a definitive diagnosis can be challenging in the absence of documented review of prior diagnostic material and clinical history.

Jak-2 positive myeloproliferative neoplasms

Originally described by Dameshek in 1951, myeloproliferative disorders are today classified as myeloproliferative Neoplasms (MPNs) in WHO's Classification of Tumors of Hematopoietic and Lymphoid Tissues. The term includes a range of conditions, [ie, BCR-ABL-positive chronic myelogenous leukemia (CML), chronic neutrophilic leukemia (CNL), polycythemia vera (PV), primary myelofibrosis (PMF), essential thromobocythemia (ET), chronic eosinophilic leukemia not otherwise specified (CEL-NOS), mastocytosis, and unclassifiable myeloproliferative neoplasm]. In the specific case of CML, a better understanding of the pathogenesis and pathophysiology of the disease has led to a targeted therapy. The presence of chromosome Philadelphia, t(9;22)(q34;11) results in the oncogene BCR-ABL, which characterizes the disease; this molecular rearrangement gives rise to a tyrosine-kinase, which in turn triggers the proliferation of the myeloid line through the activation of the signaling pathways downstream. Tyrosine-kinase inhibitors (TKIs) have altered the therapy and monitoring of CML patients and improved both their prognosis and quality of life. In 2005, various groups of investigators described a new point mutation of the gene JAK2 associated to MPNs. Although the presence of this mutation has led to a modification in the diagnostic criteria of these conditions, the impact of the use of JAK2 inhibitors on the prognosis and course of the disease continues to be controversial.

WHO classification of myeloproliferative neoplasms (MPN): A critical update

Although the revised World Health Organization (WHO) criteria for the diagnosis and classification of myeloproliferative neoplasms (MPN) were defined by a panel of expert hematopathologists and clinicians, controversy has been repeatedly expressed questioning the clinical usefulness and reproducibility of these diagnostic guidelines. In particular, the distinction between essential thrombocythemia (ET), early/prefibrotic primary myelofibrosis (PMF) and initial stages of polycythemia vera (PV) is still a matter of debate. In this context, it has been argued that clinical correlations with histological features were not firmly substantiated. On the other hand, recently published data from independently performed studies have repeatedly validated the reproducibility of the WHO criteria and provided persuasive evidence that discrimination of early/prefibrotic PMF has a significant impact on the risk of myelofibrotic and leukemic transformation. However, as has been explicitly required, the WHO concept is based on the recognition of characteristic bone marrow patterns and a consensus of clinical and molecular data.

[Differential diagnosis of myeloproliferative neoplasms. Quantitative NF-E2 immunohistochemistry for differentiating between essential thrombocythemia and primary myelofibrosis]

BACKGROUND

Besides essential thrombocythemia (ET), polycythemia vera (PV) and primary myelofibrosis (PMF) the myeloproliferative neoplasms (MPN) defined by the World Health Organization (WHO) comprise the entity of unclassifiable MPNs (MPN, U). The exact differential diagnosis of the specific MPN entities can be challenging particularly at early stages of the diseases. So far, pathologists have had to rely only on histomorphological evaluation of bone marrow biopsies in combination with laboratory data because helpful ancillary tests are not yet available. Even molecular tests, such as JAK2 mutation analysis are not helpful particularly in the differential diagnosis of ET and PMF because both entities are associated with the V617F mutation in 50 % of the cases. Recently overexpression of the transcription factor NF-E2 in MPN was described.

MATERIALS AND METHODS

A collective of samples consisting of 163 bone marrow biopsies including 139 MPN cases was stained immunohistochemically for NF-E2 and analyzed regarding the subcellular localization of NF-E2 in erythroid progenitor cells. The results were compared between the MPN entities as well as the controls and statistical analyses were conducted.

RESULTS AND DISCUSSION

This study showed that NF-E2 immunohistochemistry and analysis of the proportion of nuclear positive erythroblasts of all erythroid precursor cells can help to distinguish between ET and PMF even in early stages of the diseases. An MPN, U case showing a proportion of more than 20 % nuclear positive erythroblasts can be classified as a PMF with 92 % accuracy.

Problems and pitfalls regarding WHO-defined diagnosis of early/prefibrotic primary myelofibrosis versus essential thrombocythemia

Reproducibility and clinical usefulness of the WHO classification of chronic myeloproliferative neoplasm (MPN) persist to be a controversial issue. Major arguments are focused on the critical impact of histopathology, particularly concerning the distinction between essential thrombocythemia (ET) versus early/prefibrotic primary myelofibrosis (PMF). Regarding bone marrow morphology, WHO guidelines strictly require the recognition of characteristic histological patterns based on standardized features and a consensus of clinical and molecular-genetic data. Molecular-genetic findings as JAK2V617F, may aid to exclude reactive thrombocytosis, although in ET and PMF only 50-60% of the cases show these aberrations. Considerable doubts over the existence of early/prefibrotic PMF have been expressed with the consequence to include this entity in the ET category. On the other hand, it has to be argued that some of the critical studies failed to adhere very strictly to the WHO guidelines. Contrasting this situation, recently published retrospective and prospective clinico-pathological studies featuring the WHO criteria provided an important information on disease outcomes supporting the existence of early/prefibrotic PMF as a distinct clinico-pathologic entity in patients presenting clinically with ET. Therefore, this controversy suggests a scientific project, including the community of pathologists and hematologists, for providing sound, objective and reproducible criteria for diagnosing early/prefibrotic PMF.

Anagrelide compared with hydroxyurea in WHO-classified essential thrombocythemia: the ANAHYDRET Study, a randomized controlled trial

High platelet counts in essential thrombocythemia (ET) can be effectively lowered by treatment with either anagrelide or hydroxyurea. In 259 previously untreated, high-risk patients with ET, diagnosed according to the World Health Organization classification system, the efficacy and tolerability of anagrelide compared with hydroxyurea were investigated in a prospective randomized noninferiority phase 3 study in an a priori-ordered hypothesis. Confirmatory proof of the noninferiority of anagrelide was achieved after 6 months using the primary end point criteria and was further confirmed after an observation time of 12 and 36 months for platelet counts, hemoglobin levels, leukocyte counts (P < .001), and ET-related events (HR, 1.19 [95% CI, 0.61-2.30], 1.03 [95% CI, 0.57-1.81], and 0.92 [95% CI, 0.57-1.46], respectively). During the total observation time of 730 patient-years, there was no significant difference between the anagrelide and hydroxyurea group regarding incidences of major arterial (7 vs 8) and venous (2 vs 6) thrombosis, severe bleeding events (5 vs 2), minor arterial (24 vs 20) and venous (3 vs 3) thrombosis and minor bleeding events (18 vs 15), or rates of discontinuation (adverse events 12 vs 15 or lack of response 5 vs 2). Disease transformation into myelofibrosis or secondary leukemia was not reported. Anagrelide as a selective platelet-lowering agent is not inferior compared with hydroxyurea in the prevention of thrombotic complications in patients with ET diagnosed according to the World Health Organization system. This trial was registered at http://www.clinicaltrials.gov as #NCT01065038.

The differential diagnosis and bone marrow evaluation of new-onset pancytopenia

New-onset pancytopenia can be caused by a wide variety of etiologies, leading to a diagnostic dilemma. These etiologies range from congenital bone marrow failure to marrow space-occupying lesions, infection, and peripheral destruction, to name a few. Bone marrow examination, in addition to a detailed clinical history, is often required for an accurate diagnosis. The purpose of this review is to provide a brief overview of many of the causes of new-onset pancytopenia in adults and children, with emphasis on bone marrow findings and recommendations of additional testing and clinical evaluation when needed, with the overall aim of aiding the pathologist's role as a consultant to the patient's treating physician.

Diagnosis according to World Health Organization determines the long-term prognosis in patients with myeloproliferative neoplasms treated with anagrelide: results of a prospective long-term follow-up

OBJECTIVES

During long term follow-up of a cohort of patients with essential thrombocythemia (ET) and polycythemia vera (PV) a higher than expected incidence of myelofibrosis (MF) was noted. In order to test if the explanation could be found in the diagnostic criteria a re-evaluation of diagnosis using the 2008 WHO diagnostic criteria for ET and MF was performed.

METHODS

This prospective study of 60 patients with ET and PV was set up in 1998 to evaluate the long-term efficacy and tolerability of anagrelide treatment. Bone marrow trephine biopsies were requested from study start, after 2 and 7 years of follow-up. A blinded re-evaluation of the bone marrow trephines was performed. The 2008 WHO bone marrow criteria were used for diagnosis and fibrosis grading.

RESULTS

Of 40 patients with an initial diagnosis of ET, 21 were confirmed as 'true ET' whereas 17 were reclassified as primary myelofibrosis (PMF) (12 PMF-0, 3 PMF-1, 2 PMF-2) and 2 as myeloproliferative neoplasms of uncertain origin. After 7 years of follow-up, 19 of 21 patients with 'true ET' were alive, none had transformed to MF, leukemia, or myelodysplastic syndrome. In contrast, 4/17 patients reclassified as PMF had died, two patients transformed to myelodysplastic syndrome and 7 patients progressed to overt MF.

DISCUSSION

We conclude that a blinded re-evaluation of bone marrow trephines from study start and after 7 years of follow-up using 2008 World Health Organization criteria was able to differentiate between true ET and PMF with a marked difference in follow-up outcome.

The Association Between JAK2V617F Mutation and Bone Marrow Fibrosis at Diagnosis in Patients with Philadelphia-Negative Chronic Myeloproliferative Neoplasms

Objective: Bone marrow fibrosis is the second most common complication that causes morbidity and mortality inpatients with Philadelphia-negative myeloproliferative neoplasms (MPNs). The aim of this study was to investigate theassociation between JAK2V617F mutation and bone marrow fibrosis at diagnosis in patients with MPNs.

Material and Methods: In total, 149 patients with MPNs were retrospectively evaluated to determine if there was anassociation between the histological grade of bone marrow fibrosis and JAK2V617F mutation.

Results: In all, 67.7% of the patients carried the mutated JAK2 gene. The presence of JAK2V617F mutation was notassociated with the occurrence of bone marrow fibrosis (P=0.55) or its grade at diagnosis (P=0.65).

Conclusion: Molecular mechanisms or genetic defects other than JAK2V617F may underlie the occurrence of bonemarrow fibrosis in patients with MPNs.

Survival and disease progression in essential thrombocythemia are significantly influenced by accurate morphologic diagnosis: an international study

PURPOSE

The WHO diagnostic criteria underscore the role of bone marrow (BM) morphology in distinguishing essential thrombocythemia (ET) from early/prefibrotic primary myelofibrosis (PMF). This study examined the clinical relevance of such a distinction.

METHODS

Representatives from seven international centers of excellence for myeloproliferative neoplasms convened to create a clinicopathologic database of patients previously diagnosed as having ET (N = 1,104). Study eligibility criteria included availability of treatment-naive BM specimens obtained within 1 year of diagnosis. All bone marrows subsequently underwent a central re-review.

RESULTS

Diagnosis was confirmed as ET in 891 patients (81%) and was revised to early/prefibrotic PMF in 180 (16%); 33 patients were not evaluable. In early/prefibrotic PMF compared with ET, the 10-year survival rates (76% and 89%, respectively) and 15-year survival rates (59% and 80%, respectively), leukemic transformation rates at 10 years (5.8% and 0.7%, respectively) and 15 years (11.7% and 2.1%, respectively), and rates of progression to overt myelofibrosis at 10 years (12.3% and 0.8%, respectively) and 15 years (16.9% and 9.3%) were significantly worse. The respective death, leukemia, and overt myelofibrosis incidence rates per 100 patient-years for early/prefibrotic PMF compared with ET were 2.7% and 1.3% (relative risk [RR], 2.1; P < .001), 0.6% and 0.1% (RR, 5.2; P = .001), and 1% and 0.5% (RR, 2.0; P = .04). Multivariable analysis confirmed these findings and also identified age older than 60 years (hazard ratio [HR], 6.7), leukocyte count greater than 11 × 10(9)/L (HR, 2.01), anemia (HR, 2.95), and thrombosis history (HR, 2.81) as additional risk factors for survival. Thrombosis and JAK2V617F incidence rates were similar between the two groups. Survival in ET was similar to the sex- and age-standardized European population.

CONCLUSION

This study validates the clinical relevance of strict adherence to WHO criteria in the diagnosis of ET and provides important information on survival, disease complication rates, and prognostic factors in strictly WHO-defined ET and early/prefibrotic PMF.

Essential thrombocythemia versus early primary myelofibrosis: a multicenter study to validate the WHO classification

Controversy persists regarding the role of histopathology in the distinction between essential thrombocythemia (ET) and early-prefibrotic primary myelofi-brosis (PMF) presenting with thrombocythemia. To investigate the impact and reproducibility of bone marrow (BM) morphology according to the World Health Organization classification, 295 patients with the presumptive clinical diagnosis of either ET or early PMF were studied. Data of this cohort (Vienna group) were compared with 732 corresponding patients (Cologne group). Evaluating blindly (only age and gender known) BM specimens, the 2 groups of pathologists achieved an overall consensus of 78% regarding the total series and 88% concerning the discrimination between ET versus PMF. In 126 ET and 81 early PMF patients without pretreatment and complete documentation, a 90% concordance with the independently established clinical diagnosis was found. In 12 patients, overlapping of histopathology and some clinical findings between ET and polycythemia vera occurred. Contrasting ET, early PMF showed significant differences of presenting hematologic data and an unfavorable prognosis (estimated mean survival, 14 vs 21 years). Comparison of clinical and survival data of the Vienna cohort with the historical Cologne series revealed an overall congruence. This study highlights the impact of BM morphology for the differentiation between true vs false ET.

[A case of post-essential thrombocythemia myelofibrosis with severe osteosclerosis]

Essential thrombocythemia (ET) is a chronic myeloproliferative neoplasm that involves primarily the megakaryocytic lineage. After many years, a few patients with ET may develop bone marrow (BM) fibrosis and rarely develop osteosclerosis. A 60-yr-old female was admitted due to severe left upper quadrant abdominal discomfort. She had been diagnosed as ET 19 yrs ago. On liver computed tomography severe splenomegaly was shown. Laboratory tests revealed WBC 24.3x10(9)/L, hemoglobin 13.4 g/dL, platelets 432x10(9)/L, lactate dehydrogenase 4,065 IU/L (reference range; 240-480). Blood smear demonstrated leukoerythroblastosis, teardrop cells, and giant and hypogranular platelets. BM study revealed inadequate aspirate due to dry tap. BM biopsy showed clusters of dysplastic megakaryocytes, grade 3 fibrosis, and severe osteosclerosis. Major/minor BCR-ABL1 rearrangement and JAK2 V617F mutation were not detected. Cytogenetic studies revealed normal karyotype. According to the 2008 WHO diagnostic criteria, the patient was diagnosed as having post-essential thrombocythemia myelofibrosis with severe osteosclerosis.

Prodromal myeloproliferative neoplasms: the 2008 WHO classification

The concept of prodromal chronic myeloproliferative neoplasms has been endorsed by the WHO classification implicating a stepwise evolution of disease. Histology of the bone marrow (BM) and borderline to mildly expressed clinical features play a pivotal role for diagnosing prefibrotic-early primary myelofibrosis. By lowering the platelet count for essential thrombocythemia and regarding BM morphology, early manifestations are tackled. Pre-polycythemic stages of polycythemia vera with a low hemoglobin level at onset are diagnosed by positive JAK2V617F mutation status, a low erythropoietin value, and characteristic BM features. The revised WHO classification incorporates hematological, morphological, and molecular-genetic parameters to generate a consensus-based working diagnosis.

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.

JAK2(V617F) allele burden discriminates essential thrombocythemia from a subset of prefibrotic-stage primary myelofibrosis

OBJECTIVE

Among Philadelphia chromosome-negative myeloproliferative neoplasms (Ph(-) MPN), essential thrombocythemia (ET) and the prefibrotic phase of primary myelofibrosis (PMF) represent two subtypes with considerable overlap.

MATERIALS AND METHODS

In this study, histopathological classification of 490 MPN cases was correlated with the allelic burden of JAK2(V617F) and MPL(W515L).

RESULTS

Ph(-) MPN entities largely overlap with regard to JAK2(V617F) and MPL(W515L) allele burden, but ET displayed mutant allele burden <50%. PMF with different stages of myelofibrosis all yielded similar JAK2(V617F) allele burden. At initial presentation one-quarter of prefibrotic PMF cases exhibited an allele burden exceeding 50% (38% median JAK2(V617F) alleles, n=102). In ET, its main differential diagnosis, not a single case was found with >40% JAK2(V617F) alleles (median, 24% JAK2(V617F) alleles; n=90; p<0.001). Increase in JAK2(V617F) alleles during follow-up could not be linked to fibrosis or blastic progression but was related to polycythemic transformation in ET. MPL(W515L) was found in 3% of ET and 8% of PMF, with a significantly higher percentage of mutated alleles in fibrotic than prefibrotic PMF (median, 78% MPL(W515L) alleles; p<0.05).

CONCLUSION

Histopathological categories ET and prefibrotic PMF correlate with significant differences in mutant allelic burden of JAK2(V617F), but not of MPL(W515L) which, by contrast to JAK2(V617F), shows a higher percentage of mutated alleles in fibrotic than in prefibrotic cases. Thus, for Ph(-) MPN in which ET and prefibrotic PMF represent the most probable diagnoses, a JAK2(V617F) allele burden >50% favors a diagnosis of prefibrotic PMF.

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.

Myelofibrosis – What’s in a Name?

OBJECTIVE

Myelofibrosis (MF) implies an increase in the bone marrow (BM) fiber content without referring to quantity or quality (reticulin vs. collagen).

METHODS

This review on chronic myeloproliferative disorders is based on initial and sequential BM biopsies, clinical data and follow-up examinations. A semiquantitative grading system for MF approved by a panel of experts was applied.

RESULTS

In chronic myelogenous leukemia, minimal reticulin to advanced collagen MF is detectable at presentation in about 30% of patients. Significant correlations between BM and clinical features, but especially prognosis, are evident. Chronic idiopathic MF includes a prodromal stage showing no or little reticulin and no relevant MF with myeloid metaplasia (MMM). A stepwise evolution is demonstrable and associated with corresponding clinical data. Usually MMM is the diagnostic guideline for this disorder and consequently early stages with accompanying thrombocytosis may clinically mimic essential thrombocythemia. MF of various degrees may be observed in polycythemia vera depending on the progress of disease. Terminal stages (spent phase) reveal overt collagen corresponding with MMM. If diagnosis of essential thrombocythemia regards characteristic BM features, no relevant MF is seen at presentation and transformation into MMM is neglectable for many years.

CONCLUSION

To recognize dynamics of the disease process in chronic myeloproliferative disorders, an easily to reproduce scoring system for MF has been proposed. The clinical diagnosis of MMM does not include initial-early reticulin MF and therefore fails to detect prodromal stages.

Histological and Molecular Classification of Chronic Myeloproliferative Disorders in the Age of JAK2: Persistence of Old Questions despite New Answers

The discovery of the Janus kinase 2 gain-of-function V617F mutation (JAK2(V617F)) provided a major breakthrough in the understanding of Philadelphia chromosome-negative chronic myeloproliferative disorders (Ph(-) CMPD). Among haematologic neoplasm the mutation appears to be almost specific for Ph(-) CMPD but the different entities comprising polycythaemia vera (PV), essential thrombocythaemia and chronic idiopathic myelofibrosis (CIMF) are not discriminated by the mutation. It is unclear how the diversity with heterogeneous clinical and pathoanatomical presentations comes about. It has been suggested that differences in JAK2(V617F) gene dosage or different degrees to which the haematologic lineages are affected by the mutation could explain the heterogeneity of morphology and prognosis. Indeed the mutation mediates a PV-like phenotype but with regard to myelofibrosis JAK2(V617F) does not appear to be a causative factor. Megakaryocytes are homozygous in the majority of fibrotic CIMF and PV, whereas JAK2(V617F) heterozygosity is predominantly encountered in prefibrotic CIMF and essential thrombocythaemia but transition from hetero- to homozygosity with onset of fibrosis is rare. In conclusion, JAK2(V617F) provides a valuable adjunct to the diagnosis of Ph(-) CMPD, in particular with regard to discrimination from reactive proliferations, but the challenge of correct subtyping and hence prognostication persists for clinicians and bone marrow pathologists.

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.

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.

Polycythemia Vera: New Clinicopathologic Perspectives

Context.—Polycythemia vera (PV) is a clonal myeloproliferative disease characterized by an erythroid dominant trilineage proliferation of hematopoietic precursor cells. Classified as a chronic myeloproliferative disease, PV represents a histopathologic spectrum of 2 recognized stages, the polycythemic and postpolycythemic phase. The clinical manifestations of hemorrhage, thrombosis, and increased red cell mass are directly related to primary bone marrow dysfunction. Prognosis is strongly associated with thrombosis risk and disease progression; thus, treatment is directed toward minimizing coagulopathic complications and preventing leukemic transformation. Recently, a specific point mutation in the Janus kinase 2 (JAK2) gene was described in a majority of PV patients. The potential diagnostic and/or prognostic value of JAK2V617F is discussed.

Objective.—To review important developments from the recent and historical literature. Modern diagnostic criteria and emerging molecular findings are emphasized.

Data Sources.—A comprehensive review was performed of the relevant literature indexed in PubMed (National Library of Medicine) and referenced medical texts.

Conclusions.—Modified clinical, histologic, and laboratory criteria have clarified the diagnosis of PV. Also, continuing studies on the recently discovered JAK2V617F gene mutation may significantly improve our understanding of PV pathogenesis and facilitate its medical management.

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.

Bone Marrow Histopathology in Myeloproliferative Disorders—Current Diagnostic Approach

Current diagnostic issues in chronic myeloproliferative disorders (MPDs) include the differentiation of essential thrombocythemia (ET) from its mimics: early (prefibrotic) stages of chronic idiopathic myelofibrosis (CIMF) and early polycythemia vera (PV), both of which can be associated with thrombocytosis. Applying a systematic evaluation of bone marrow histopathology, in accordance with the current World Health Organization (WHO) classification system, it is possible to identify cases of true ET as opposed to false ET, usually early-stage CIMF accompanied by an excess of platelets. This distinction is important because the frequency of complications such as progression to overt myelofibrosis, blastic crisis, and overall prognosis are significantly different in the two conditions. The diagnostic criteria of the Polycythemia Vera Study Group (PVSG) do not adequately define the initial stages of PV, nor do they distinguish PV with thrombocytosis from ET. Differentiation of the two is possible by bone marrow histopathology, which also is highly predictive (96%) in distinguishing PV from secondary polycythemia. In conclusion, bone marrow biopsy is an important diagnostic tool for distinguishing specific subtypes of MPD and should be a mandatory step for entry evaluation and follow-up of patients enrolled in prospective studies and/or clinical trials.