Bone marrow histopathology following cytoreductive therapy in chronic idiopathic myelofibrosis

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.

Long-term effects of ruxolitinib versus best available therapy on bone marrow fibrosis in patients with myelofibrosis

BACKGROUND

Myelofibrosis (MF) is a life-shortening complication of myeloproliferative neoplasms associated with ineffective hematopoiesis, splenomegaly, and progressive bone marrow (BM) fibrosis. The oral Janus kinase (JAK) 1/JAK2 inhibitor ruxolitinib has been shown to improve splenomegaly, symptom burden, and overall survival in patients with intermediate-2 or high-risk MF compared with placebo or best available therapy (BAT).

METHODS

The effects of ruxolitinib therapy for up to 66 months on BM morphology in 68 patients with advanced MF with variable BM fibrosis grade were compared with those in 192 matching patients treated with BAT. Available trephine biopsies underwent independent, blinded review by three hematopathologists for consensus-based adjudication of grades for reticulin fibrosis, collagen deposition, and osteosclerosis.

RESULTS

Ruxolitinib treatment versus BAT was associated with greater odds of BM fibrosis improvement or stabilization and decreased odds of BM fibrosis worsening based on changes from baseline in reticulin fibrosis grade. Generally, these changes were accompanied by a sustained higher level of individual spleen size reduction and regression of leukoerythroblastosis. Patients with more advanced baseline fibrosis showed lower spleen size response.

CONCLUSIONS

The finding that long-term ruxolitinib therapy may reverse or markedly delay BM fibrosis progression in advanced MF suggests that sustained JAK inhibition may be disease-modifying.

TRIAL REGISTRATION

INCB18424-251, ClinicalTrials.gov identifier NCT00509899 .

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.

Cytokine Expression Pattern in Bone Marrow Microenvironment after Allogeneic Stem Cell Transplantation in Primary Myelofibrosis

The only curative therapy for primary myelofibrosis (PMF) is allogeneic stem cell transplantation (ASCT). However, although we know that patients can benefit from ASCT, we do not know the extent of the changes of the expression profile of cytokines and matrix modulation factors. In this first systematic analysis, we evaluated the expression profile of 103 factors before and after transplantation to identify potential biomarkers. The expression of fibrosis-, inflammation-, and angiogenesis-associated genes was analyzed in a total of 52 bone marrow biopsies: PMF patients (n = 14) before and after ASCT and, for control purposes, post-ASCT multiple myeloma patients (n = 14) and non-neoplastic hematopoiesis (n = 10). In post-ASCT PMF cases, decreased expression of tissue inhibitor of metalloproteinases (TIMP) and platelet-derived growth factor alpha (PDGFA) correlated with bone marrow remodeling and hematological remission. Expression of several other matrix factors remained at high levels and may contribute to post-ASCT remodeling. This is the first systematic analysis of cytokine expression in post-ASCT PMF bone marrow that shows that normalization of bone marrow microenvironment is paralleled by decreased expression of TIMP and PDGFA.

Fibrogenesis in Primary Myelofibrosis: Diagnostic, Clinical, and Therapeutic Implications

Primary myelofibrosis is a stem cell-derived clonal malignancy characterized by unchecked proliferation of myeloid cells, resulting in bone marrow fibrosis, osteosclerosis, and pathologic angiogenesis. Bone marrow fibrosis (BMF) plays a central role in the pathophysiology of the disease. This review describes current issues regarding BMF in primary myelofibrosis, including the pathophysiology and impact of abnormal deposition of excess collagen and reticulin fibers in bone marrow spaces, the modified Bauermeister and the European Consensus grading systems of BMF, and the prognostic impact of BMF on the overall outcome of patients with primary myelofibrosis. The impact of novel therapeutic strategies, including JAK-STAT inhibitors and allogeneic stem cell transplant, on BMF is discussed.

High concordance in grading reticulin fibrosis and cellularity in patients with myeloproliferative neoplasms

The myeloproliferative neoplasms primary myelofibrosis, polycythemia vera, and, rarely, essential thrombocythemia are characterized by variable degrees of bone marrow fibrosis, either at presentation or upon progression. The increasing use of emerging therapies that may alter disease biology and morphology demands accurate and reproducible assessment of fibrosis grade. To assess concordance of hematopoietic cellularity and fibrosis grading, three hematopathologists independently evaluated a total of 728 bone marrow biopsies from 261 patients with myeloproliferative neoplasms on three clinical trials using fedratinib (SAR302503), a JAK2 inhibitor, including 249 taken at baseline and 479 on therapy. Concordance between the pathologists was evaluated by Pearson correlation coefficient (cellularity) and unweighted kappa statistic (fibrosis grade). There was high correlation of cellularity assessment (r=0.92) and fibrosis grading (kappa=0.83) between the three pathologists. Concordance with World Health Organization (WHO) grade 3 samples was higher compared with grades 0, 1, and 2. Concordance of fibrosis grading in pretreatment samples was superior to that of post-treatment samples (kappa=0.83 and 0.79, respectively, P=0.023). Our analysis suggests that the updated 2008 WHO reticulin fibrosis grading system is highly reproducible, even in patients undergoing JAK2 inhibitor therapy. This system is practically applicable to establish baseline fibrosis grade as well as changes in fibrosis in subsequent samples on therapy.

Reversible bone marrow aplasia induced by pegylated interferon-α-2a therapy in a patient with primary myelofibrosis

Interferon has been widely used in the management of patients with hematological malignancies such as polycythemia vera, myelofibrosis, chronic myeloid leukemia and viral infections such as chronic hepatitis C. Hematological adverse effects such as cytopenias have been observed, particularly in patients who receive a combination of interferon-α-2a and ribavirin for hepatitis C. Mild myelosuppression can be seen with pegylated interferon; however, bone marrow aplasia in patients with myelofibrosis has not been reported. It is important to be aware of such a serious complication since persistent bone marrow aplasia can be fatal. We describe a case of pegylated interferon-induced reversible bone marrow aplasia in a patient with primary myelofibrosis.

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.

Correlation of histopathological findings and magnetic resonance imaging in the spine of patients with ankylosing spondylitis

Ankylosing spondylitis (AS) is a chronic inflammatory disease which affects primarily the sacroiliac joints and the spine. In patients with active disease, magnetic resonance imaging (MRI) of the spine shows areas of bone marrow edema, the histopathological equivalent of which is unknown. In this study we correlate inflammation in the spine of patients with AS as revealed by histological examination with bone marrow edema as detected by MRI. We have compared the histopathological findings of zygapophyseal joints from 8 patients with AS (age: 30 to 64, disease duration 7 to 33 years) undergoing spinal surgery with findings in MRI. For histopathological analysis, we quantified infiltrates of CD3+, CD4+ and CD8+ T cells as well as CD20+ B cells immunohistochemically. Bone marrow edema was evaluated in hematoxylin and eosin stained sections and quantified as the percentage of the bone marrow area involved. All patients with AS showed interstitial mononuclear cell infiltrates and various degrees of bone marrow edema (range from 10% to 60%) in histopathological analysis. However, in only three of eight patients histopathological inflammation and edema in the zygapophyseal joints correlated with bone marrow edema in zygapophyseal joints of the lumbar spine as detected by MRI. Interestingly, two of these patients showed the highest histological score for bone marrow edema (60%). This first study correlating histopathological changes in the spine of patients with AS with findings in MRI scans suggests that a substantial degree of bone marrow inflammation and edema is necessary to be detected by MRI.

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.

Morphology of the bone marrow after stem cell transplantation

In many haematological conditions the only curative option is stem cell (SCT) or bone marrow (BM) transplantation. Little information exists about BM morphology following non-ablative engraftment. During the pretransplantation period and depending on the kind of pretreatment, there may be hypoplasia, residual disease and varying degrees of fibrosis. In the post-transplantation period, after 1-3 weeks of transfusion-dependent pancytopenia, the first signs of successful engraftment are indicated by the recurrence of neutrophils, monocytes and erythrocytes in the peripheral blood. In the BM there is slow regeneration of erythropoiesis, followed by the other lineages of haematopoiesis and increase in reticulin fibres or even a resolution of fibrosis. Diagnostic problems arise when neoplastic lympho- or haematopoiesis are maintained following transplantation. Moreover, there may be a significant graft versus tumour response reaction or an already relapsing disease needing aggressive treatment. On the other hand, a conspicuous dyshaematopoiesis should not be mistaken as representing a myelodysplastic syndrome. The presence of granulomas being treatment-related or a manifestation of intercurrent granulomatous disease has to be considered. More advanced knowledge of the histological features of regenerating BM will certainly aid the recognition of relapsing disease and is needed for the adequate reporting of post-transplant alterations associated with a successful or failing engraftment.

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.

Pilot study of reduced-intensity conditioning followed by allogeneic stem cell transplantation from related and unrelated donors in patients with myelofibrosis

A prospective pilot study was performed to evaluate the effect of reduced-intensity conditioning with busulphan (10 mg/kg), fludarabine (180 mg/qm) and anti-thymocyte globulin followed by allogeneic stem cell transplantation from related (n = 8) and unrelated donors (n = 13) in 21 patients with myelofibrosis. The median age of the patients was 53 years (range, 32-63). No primary graft failure occurred. The median time until leucocyte (>1.0 x 10(9)/l) and platelet (>20 x 10(9)/l) engraftment was 16 (range, 11-26) and 23 d (range, 9-139) respectively. Complete donor chimaerism on day 100 was seen in 20 patients (95%). Acute graft-versus-host disease (GvHD) grades II-IV and III/IV occurred in 48% and 19% of cases and 55% of the patients had chronic GvHD. Treatment-related mortality was 0% at day 100 and 16% [95% confidence interval (CI): 0-32%] at 1 year. Haematological response was seen in 100% and complete histopathological remission was observed in 75% of the patients and 25% of the patients showed partial histopathological remission with a continuing decline in the grade of fibrosis. After a median follow-up of 22 months (range, 4-59), the 3-year estimated overall and disease-free survival was 84% (95% CI: 67-100%).