Different niches for stem cells carrying the same oncogenic driver affect pathogenesis and therapy response in myeloproliferative neoplasms.

Aging facilitates the expansion of hematopoietic stem cells (HSCs) carrying clonal hematopoiesis-related somatic mutations and the development of myeloid malignancies, such as myeloproliferative neoplasms (MPNs). While cooperating mutations can cause transformation, it is unclear whether distinct bone marrow (BM) HSC-niches can influence the growth and therapy response of HSCs carrying the same oncogenic driver. Here we found different BM niches for HSCs in MPN subtypes. JAK-STAT signaling differentially regulates CDC42-dependent HSC polarity, niche interaction and mutant cell expansion. Asymmetric HSC distribution causes differential BM niche remodeling: sinusoidal dilation in polycythemia vera and endosteal niche expansion in essential thrombocythemia. MPN development accelerates in a prematurely aged BM microenvironment, suggesting that the specialized niche can modulate mutant cell expansion. Finally, dissimilar HSC-niche interactions underpin variable clinical response to JAK inhibitor. Therefore, HSC-niche interactions influence the expansion rate and therapy response of cells carrying the same clonal hematopoiesis oncogenic driver.

Survey of UK histopathology consultants' attitudes towards academic and molecular pathology.

OBJECTIVE: Academic pathology is facing a crisis; an ongoing decline in academic pathology posts, a paucity of academic pathologist's in-training and unfilled posts at a time when cellular pathology departments are challenged to deliver increasing numbers of molecular tests. The National Cancer Research Institute initiative in Cellular & Molecular Pathology commissioned a survey to assess attitudes of cellular pathology consultants towards research in order to understand barriers and identify possible solutions to improve this situation. As cellular pathology is encompassing an increasing number of diagnostic molecular tests, we also surveyed the current approach to and extent of training in molecular pathology. METHODS: The survey was distributed to all UK-based consultant pathologists via the Pathological Society of Great Britain & Ireland and Royal College of Pathologist networks. Heads of Department were contacted separately to obtain figures for number of academic training and consultant posts. RESULTS: 302 cellular pathologists completed the survey which represents approximately 21% of the total cellular histopathology workforce. Most respondents (89%) had been involved in research at some point; currently, 22% were undertaking research formally, and 41% on an informal basis. Of those previously involved in research, 57% stopped early in their consultant career. The majority of substantive academic posts were Professors of which 60% had been in post for >20 years. Most respondents (84%) used molecular pathology in diagnostic work, independent of where they worked or the length of time in post. Notably, 53% of consultants had not received molecular pathology training, particularly more senior consultants and consultants in district general hospitals. CONCLUSIONS: The survey reveals that the academic workforce is skewed towards senior individuals, many of whom are approaching retirement, with a missing cohort of 'junior consultant' academic pathologists to replace them. Most pathologists stop formal research activity at the beginning of a consultant career. While molecular pathology is an increasing part of a pathologist's workload, the majority of consultant cellular pathologists have not received any formal molecular training.

Hydroxycarbamide Plus Aspirin Versus Aspirin Alone in Patients With Essential Thrombocythemia Age 40 to 59 Years Without High-Risk Features.

PURPOSE: Cytoreductive therapy is beneficial in patients with essential thrombocythemia (ET) at high risk of thrombosis. However, its value in those lacking high-risk features remains unknown. This open-label, randomized trial compared hydroxycarbamide plus aspirin with aspirin alone in patients with ET age 40 to 59 years and without high-risk factors or extreme thrombocytosis. PATIENTS AND METHODS: Patients were age 40 to 59 years and lacked a history of ischemia, thrombosis, embolism, hemorrhage, extreme thrombocytosis (platelet count ≥ 1,500 × 109/L), hypertension, or diabetes requiring therapy. In all, 382 patients were randomly assigned 1:1 to hydroxycarbamide plus aspirin or aspirin alone. The composite primary end point was time to arterial or venous thrombosis, serious hemorrhage, or death from vascular causes. Secondary end points were time to first arterial or venous thrombosis, first serious hemorrhage, death, incidence of transformation, and patient-reported quality of life. RESULTS: After a median follow-up of 73 months and a total follow-up of 2,373 patient-years, there was no significant difference between the arms in the likelihood of patients reaching the primary end point (hazard ratio, 0.98; 95% CI, 0.42 to 2.25; P = 1.0). The incidence of significant vascular events was low, at 0.93 per 100 patient-years (95% CI, 0.61 to 1.41). There were also no differences in overall survival; in the composite end point of transformation to myelofibrosis, acute myeloid leukemia, or myelodysplasia; in adverse events; or in patient-reported quality of life. CONCLUSION: In patients with ET age 40 to 59 years and lacking high-risk factors for thrombosis or extreme thrombocytosis, preemptive addition of hydroxycarbamide to aspirin did not reduce vascular events, myelofibrotic transformation, or leukemic transformation. Patients age 40 to 59 years without other clinical indications for treatment (such as previous thrombosis or hemorrhage) who have a platelet count < 1,500 × 109/L should not receive cytoreductive therapy.

Management of polycythaemia vera: a critical review of current data.

Polycythaemia vera (PV) is a chronic blood cancer; its clinical features are dominated by myeloproliferation (erythrocytosis, often leucocytosis and/or thrombocytosis) and a tendency for thrombosis and transformation to myelofibrosis or acute myeloid leukaemia. In the past 10 years the pathophysiology of this condition has been defined as JAK/STAT pathway activation, almost always due to mutations in JAK2 exons 12 or 14 (JAK2 V617F). In the same time period our understanding of the optimal management of PV has expanded, most recently culminating in the approval of JAK inhibitors for the treatment of PV patients who are resistant or intolerant to therapy with hydroxycarbamide. It has also been demonstrated that life expectancy for many patients with PV is not normal, nor is their quality of life. We critically explore these findings and discuss their impact. In addition, we highlight persisting gaps in our current management strategy; for example, what is the optimal first line cytoreductive therapy and, indeed, which patients need cytoreductive drugs.

How we diagnose and treat essential thrombocythaemia.

The approach to the diagnosis and management of essential thrombocythaemia (ET) is steadily changing, influenced by advances in molecular biology, data from clinical trials and retrospective analyses of patient cohorts. In the past decade options for clinical management largely remain unchanged, but who we treat, and with what target in mind, is evolving. A further area of change is recognition of symptoms that may be associated with ET, as well as other myeloproliferative neoplasms, and that potential options for their management are becoming available. Judicious and careful diagnosis is increasingly a fundamental key to successful management followed by cytoreductive therapy in a subset of patients. In this review we demonstrate our management strategies for ET using a case-based format.

Resolution of bone marrow fibrosis in a patient receiving JAK1/JAK2 inhibitor treatment with ruxolitinib.

UNLABELLED: Ruxolitinib, a JAK1/JAK2 inhibitor, is currently the only pharmacological agent approved for the treatment of myelofibrosis. Approval was based on findings from two phase 3 trials comparing ruxolitinib with placebo (COMFORT-I) and with best available therapy (COMFORT-II) for the treatment of primary or secondary myelofibrosis. In those pivotal trials, ruxolitinib rapidly improved splenomegaly, disease-related symptoms, and quality of life and prolonged survival compared with both placebo and conventional treatments. However, for reasons that are currently unclear, there were only modest histomorphological changes in the bone marrow, and only a subset of patients had significant reductions in JAK2 V617F clonal burden. Here we describe a patient with post-polycythemia vera myelofibrosis who received ruxolitinib at our institution (Guy's and St. Thomas' NHS Foundation Trust, London, United Kingdom) as part of the COMFORT-II study. While on treatment, the patient had dramatic improvements in splenomegaly and symptoms shortly after starting ruxolitinib. With longer treatment, the patient had marked reductions in JAK2 V617F allele burden, and fibrosis of the bone marrow resolved after approximately 3 years of ruxolitinib treatment. To our knowledge, this is the first detailed case report of resolution of fibrosis with a JAK1/JAK2 inhibitor. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT00934544.

Fluorescence in situ hybridisation analysis of formalin-fixed paraffin-embedded tissue sections in the diagnostic work-up of non-Burkitt high grade B-cell non-Hodgkin's lymphoma: a single centre's experience.

AIMS: In recent years the genetic aberrations associated with diffuse large B-cell lymphoma and the new subtype described in the 2008 revision of the WHO classification, 'B-cell lymphoma, unclassifiable, with features intermediate between diffuse large B-cell lymphoma and Burkitt lymphoma' have been increasingly well defined. Recurrent genetic abnormalities include rearrangements involving MYC (8q24), BCL2 (18q21) and BCL6 (3q27); as the prognostic and therapeutic implications associated with these abnormalities are clarified their accurate identification at diagnosis is becoming increasingly critical. We describe our experience of using a panel of fluorescence in situ hybridisation (FISH) probes on formalin-fixed paraffin-embedded tissue sections in the diagnostic work-up of 162 patients with non-Burkitt high grade B-cell non-Hodgkin's lymphomas (HG-BNHL). METHODS: BCL6, IGH-BCL2 and MYC status were determined prospectively in sequential patients presenting with HG-BNHL, with respect to the presence of rearrangements and copy number changes. Small numbers of samples were analysed retrospectively or were studied at relapse in previously untested patients. RESULTS: FISH analysis was successful in 160/162 (99%) cases, with abnormalities detected in 118/160 (74%). CONCLUSIONS: FISH analysis of formalin-fixed paraffin-embedded tissue sections is a highly reproducible technique with an excellent success rate for the detection of genetic abnormalities which will play an increasingly important role in improving risk stratification of patients with HG-BNHL.

Pitfalls in bone marrow pathology: avoiding errors in bone marrow trephine biopsy diagnosis.

Avoiding errors in the histological interpretation of bone marrow trephine biopsy specimens requires an unprecedented degree of collaboration between histopathologists, haematologists, specimen requesters, specimen takers, laboratory technical staff and other scientific staff. A specimen of good quality, with full, relevant clinical information is the essential starting point. This must then be processed optimally and investigated appropriately, involving immunophenotyping and molecular testing when needed. A wide range of pathologies may involve bone marrow haemopoietic and stromal components, and a systematic approach to analysing each of the components in turn is required to avoid overlooking abnormalities; correlation with bone marrow cells aspirated in parallel is particularly important. Final interpretation should be a synthesis of the histological findings with information from such haematological and other investigations, interpreted with due regard to clinical context.

Pitfalls in lymphoma pathology: avoiding errors in diagnosis of lymphoid tissues.

The complexity involved in the histological interpretation of lymph nodes and other lymphoid tissue specimens suspected of harbouring lymphoma is underappreciated. As with other histology specimens, the quality of sections and background information are crucial but so, increasingly, is the appropriate use of immunocytochemistry and a variety of molecular analyses. Within the UK National Health Service, progressive regional centralisation is ongoing, to ensure access to specialist expertise and a full range of testing beyond traditional stains. This is to be welcomed but there remains a need to maintain skills in smaller district hospitals, to ensure lymphoma recognition in unexpected circumstances, to permit clinically useful interim diagnoses when needed urgently and to sustain training in haematopathology among junior pathologists. In this review a range of potential pitfalls in lymphoid tissue pathology is outlined, arising at all stages from specimen preparation to reporting. Knowledge of such pitfalls, some of which are common while others are rare but of vital clinical importance, should help increase confidence in lymphoma diagnosis among histopathologists.

Making the most of bone marrow trephine biopsy.

Bone marrow trephine biopsy is an integral component of the diagnosis, staging and follow-up of many haematological diseases. Adequate size and integrity of the initial specimen are crucial, although data defining what constitutes an adequate sample in different clinical contexts are limited. The requirement for decalcification or plastic embedding during tissue processing poses additional challenges for histological quality and successful application of essential techniques, including immunohistochemistry, DNA/RNA in situ hybridization and polymerase chain reaction. These challenges, however, can be addressed by careful attention to technical methods, some of which require modification from standard methods applied to other tissues in histopathology laboratories. Individuals reporting bone marrow trephine specimens must have sufficient understanding of haematopoietic and stromal components, and how these are affected by a wide range of diseases, to extract maximum information to support clinical decisions. This includes recognition of the need to consider results from peripheral blood, aspirated bone marrow and imaging studies, in the context of full clinical details, when assessing bone marrow histology. In different organizational settings, histopathologists or haematologists appropriately take primary responsibility for bone marrow trephine reporting or work conjointly: there is no area of clinical pathology in which an integrated, multidisciplinary approach is more important or rewarding.

Reticulin accumulation in essential thrombocythemia: prognostic significance and relationship to therapy.

PURPOSE: Essential thrombocythemia (ET) manifests substantial interpatient heterogeneity in rates of thrombosis, hemorrhage, and disease transformation. Bone marrow histology reflects underlying disease activity in ET but many morphological features show poor reproducibility. PATIENTS AND METHODS: We evaluated the clinical significance of bone marrow reticulin, a measure previously shown to have relatively high interobserver reliability, in a large, prospectively-studied cohort of ET patients. RESULTS: Reticulin grade positively correlated with white blood cell (P = .05) and platelet counts (P = .0001) at diagnosis. Elevated reticulin levels at presentation predicted higher rates of arterial thrombosis (hazard ratio [HR], 1.8; 95% CI, 1.1 to 2.9; P = .01), major hemorrhage (HR, 2.0; 95% CI, 1.0 to 3.9; P = .05), and myelofibrotic transformation (HR, 5.5; 95% CI, 1.7 to 18.4; P = .0007) independently of known risk factors. Higher reticulin levels at diagnosis were associated with greater subsequent falls in hemoglobin levels in patients treated with anagrelide (P < .0001), but not in those receiving hydroxyurea (P = .9). Moreover, serial trephine specimens in patients randomly assigned to anagrelide showed significantly greater increases in reticulin grade compared with those allocated to hydroxyurea (P = .0003), and four patients who developed increased bone marrow reticulin on anagrelide showed regression of fibrosis when switched to hydroxyurea. These data suggest that patients receiving anagrelide therapy should undergo surveillance bone marrow biopsy every 2 to 3 years and that those who show substantially increasing reticulin levels are at risk of myelofibrotic transformation and may benefit from changing therapy before adverse clinical features develop. CONCLUSION: Our results demonstrate that bone marrow reticulin grade at diagnosis represents an independent prognostic marker in ET, reflecting activity and/or duration of disease, with implications for the monitoring of patients receiving anagrelide.

MPL mutations in myeloproliferative disorders: analysis of the PT-1 cohort.

Activating mutations of MPL exon 10 have been described in a minority of patients with idiopathic myelofibrosis (IMF) or essential thrombocythemia (ET), but their prevalence and clinical significance are unclear. Here we demonstrate that MPL mutations outside exon 10 are uncommon in platelet cDNA and identify 4 different exon 10 mutations in granulocyte DNA from a retrospective cohort of 200 patients with ET or IMF. Allele-specific polymerase chain reaction was then used to genotype 776 samples from patients with ET entered into the PT-1 studies. MPL mutations were identified in 8.5% of JAK2 V617F(-) patients and a single V617F(+) patient. Patients carrying the W515K allele had a significantly higher allele burden than did those with the W515L allele, suggesting a functional difference between the 2 variants. Compared with V617F(+) ET patients, those with MPL mutations displayed lower hemoglobin and higher platelet levels at diagnosis, higher serum erythropoietin levels, endogenous megakaryocytic but not erythroid colony growth, and reduced bone marrow erythroid and overall cellularity. Compared with V617F(-) patients, those with MPL mutations were older with reduced bone marrow cellularity but could not be identified as a discrete clinicopathologic subgroup. MPL mutations lacked prognostic significance with respect to thrombosis, major hemorrhage, myelofibrotic transformation or survival.

Bone marrow pathology in essential thrombocythemia: interobserver reliability and utility for identifying disease subtypes.

The role of histopathology in the diagnosis of essential thrombocythemia (ET) is controversial, and there has been little attempt to quantitate interobserver variability. Diagnostic bone marrow trephine biopsy specimens from 370 patients with ET by Polycythemia Vera Study Group (PVSG) criteria were assessed by 3 experienced hematopathologists for 16 different morphologic features and overall diagnosis according to the World Health Organization (WHO) classification. Our results show substantial interobserver variability, particularly for overall diagnosis and individual cellular characteristics such as megakaryocyte morphology. Reticulin grade was the dominant independent predictor of WHO diagnostic category for all 3 hematopathologists. Factor analysis identified 3 independent factors likely to reflect underlying biologic processes. One factor related to overall and lineage-specific cellularity and was significantly associated with JAK2 V617F status (P < .001), a second factor related to megakaryocyte clustering, and a third was associated with the fibrotic process. No differences could be discerned between patients labeled as having "prefibrotic myelofibrosis" or "true ET" in clinical and laboratory features at presentation, JAK2 status, survival, thrombosis, major hemorrhage, or myelofibrotic transformation. These results show that histologic criteria described in the WHO classification are difficult to apply reproducibly and question the validity of distinguishing true ET from prefibrotic myelofibrosis on the basis of subjective morphologic criteria. This study was registered at http://isrctn.org as #72251782 and at http://eudract.emea.europa.eu/ as #2004-000245-38.

Cutaneous extramedullary hemopoiesis in chronic myeloproliferative and myelodysplastic disorders.

Cutaneous extramedullary hemopoiesis (EMH) is a rare complication of chronic myeloproliferative and myelodysplastic disorders. Chronic idiopathic myelofibrosis (CIMF) is the most common underlying condition. To date, fewer than 30 cases have been reported in the literature and there has been significant confusion with regard to the proposed pathogenesis. In this article, we describe two additional cases of cutaneous EMH associated with chronic myeloid diseases and review the literature with the aim of clarifying the underlying pathogenesis of this unusual clinical condition. The diagnosis of cutaneous EMH in both patients with chronic myeloid diseases was made histopathologically, with immunohistochemistry confirming the presence of differentiating hemopoietic cells associated with dermal components. Cutaneous EMH in chronic myeloid diseases occurs as a result of migration of abnormal neoplastic hemopoietic precursor cells into the skin (in effect, metastasis) and subsequent differentiation along divergent myeloid cell lineages. The diagnosis should be considered in any patient with chronic myeloproliferative or myelodysplastic disease who develops a skin rash.

Definition of subtypes of essential thrombocythaemia and relation to polycythaemia vera based on JAK2 V617F mutation status: a prospective study.

BACKGROUND: An acquired V617F mutation in JAK2 occurs in most patients with polycythaemia vera, but is seen in only half those with essential thrombocythaemia and idiopathic myelofibrosis. We aimed to assess whether patients with the mutation are biologically distinct from those without, and why the same mutation is associated with different disease phenotypes. METHODS: Two sensitive PCR-based methods were used to assess the JAK2 mutation status of 806 patients with essential thrombocythaemia, including 776 from the Medical Research Council's Primary Thrombocythaemia trial (MRC PT-1) and two other prospective studies. Laboratory and clinical features, response to treatment, and clinical events were compared for V617F-positive and V617F-negative patients with essential thrombocythaemia. FINDINGS: Mutation-positive patients had multiple features resembling polycythaemia vera, with significantly increased haemoglobin (mean increase 9.6 g/L, 95% CI 7.6-11.6 g/L; p<0.0001), neutrophil counts (1.1x10(9)/L, 0.7-1.5x10(9)/L; p<0.0001), bone marrow erythropoiesis and granulopoiesis, more venous thromboses, and a higher rate of polycythaemic transformation than those without the mutation. Mutation-positive patients had lower serum erythropoietin (mean decrease 13.8 U/L; 95% CI, 10.8-16.9 U/L; p<0.0001) and ferritin (n=182; median 58 vs 91 mug/L; p=0.01) concentrations than did mutation-negative patients. Mutation-negative patients did, nonetheless, show many clinical and laboratory features that were characteristic of a myeloproliferative disorder. V617F-positive individuals were more sensitive to therapy with hydroxyurea, but not anagrelide, than those without the JAK2 mutation. INTERPRETATION: Our results suggest that JAK2 V617F-positive essential thrombocythaemia and polycythaemia vera form a biological continuum, with the degree of erythrocytosis determined by physiological or genetic modifiers.

Hydroxyurea compared with anagrelide in high-risk essential thrombocythemia.

BACKGROUND: We conducted a randomized comparison of hydroxyurea with anagrelide in the treatment of essential thrombocythemia. METHODS: A total of 809 patients with essential thrombocythemia who were at high risk for vascular events received low-dose aspirin plus either anagrelide or hydroxyurea. The composite primary end point was the actuarial risk of arterial thrombosis (myocardial infarction, unstable angina, cerebrovascular accident, transient ischemic attack, or peripheral arterial thrombosis), venous thrombosis (deep-vein thrombosis, splanchnic-vein thrombosis, or pulmonary embolism), serious hemorrhage, or death from thrombotic or hemorrhagic causes. RESULTS: After a median follow-up of 39 months, patients in the anagrelide group were significantly more likely than those in the hydroxyurea group to have reached the primary end point (odds ratio, 1.57; 95 percent confidence interval, 1.04 to 2.37; P=0.03). As compared with hydroxyurea plus aspirin, anagrelide plus aspirin was associated with increased rates of arterial thrombosis (P=0.004), serious hemorrhage (P=0.008), and transformation to myelofibrosis (P=0.01) but with a decreased rate of venous thromboembolism (P=0.006). Patients receiving anagrelide were more likely to withdraw from their assigned treatment (P<0.001). Equivalent long-term control of the platelet count was achieved in both groups. CONCLUSIONS: Hydroxyurea plus low-dose aspirin is superior to anagrelide plus low-dose aspirin for patients with essential thrombocythemia at high risk for vascular events.