Bone marrow features and clinical findings in chronic myeloid leukemia--a comparative, multicenter, immunohistological and morphometric study on 614 patients

Differential diagnoses and the mutational landscape of myelodysplastic/myeloproliferative neoplasm with neutrophilia: A case report

Myelodysplastic/myeloproliferative neoplasm with neutrophilia (MDS/MPN-N; previously referred to as atypical chronic myeloid leukemia) is a type of myelodysplastic syndrome/myeloproliferative neoplasm. A molecular genetic precondition for diagnosis is BCR::ABL negativity; further diagnostic criteria include clinicopathological assessments, such as peripheral blood leukocyte counts, the number of neutrophils and their precursors, and the presence of dysgranulopoiesis. The present case report highlights the importance of differential diagnoses with a stringent diagnostic workup according to the 5th Edition of the World Health Organization Classification of Hematolymphoid Tumors. A systematic review of the literature from 2013 to 2022 covering the mutational landscape of MDS/MPN-N was also performed to highlight recent improvements in the molecular genetic diagnostics of this disease.

International Consensus Classification of myeloid and lymphoid neoplasms: myeloproliferative neoplasms

The recently published International Consensus Classification (ICC) of myeloid neoplasms summarized the results of an in-depth effort by pathologists, oncologists, and geneticists aimed to update the 2017 World Health Organization classification system for hematopoietic tumors. Along these lines, several important modifications were implemented in the classification of myeloproliferative neoplasms (MPNs). For chronic myeloid leukemia, BCR::ABL1-positive, the definition of accelerated and blast phase was simplified, and in the BCR::ABL1-negative MPNs, the classification was slightly updated to improve diagnostic specificity with a more detailed and better validated morphologic approach and the recommendation of more sensitive molecular techniques to capture in particular early stage diseases. In this regard, high sensitive single target (RT-qPCR, ddPCR) or multi-target next-generation sequencing assays with a minimal sensitivity of VAF 1% are now important for a proper diagnostic identification of MPN cases with low allelic frequencies at initial presentation. This review discusses the updated diagnostic criteria of MPN according to the ICC, particularly by highlighting the new concepts and how they can be applied in clinical settings to obtain an appropriate prognostic relevant diagnosis.

Paediatric chronic myeloid leukaemia: Is it really a different disease?

Paediatric chronic myeloid leukaemia (CML) has biological and clinical differences from adult CML. Management of paediatric CML presents unique challenges in growing children, and there are no specific guidelines for paediatric CML. This review focusses on the clinical characteristics, diagnostic issues and management of paediatric CML. Major studies that provide the basis of managing paediatric CML are summerized here. Studies conducted on adult CML patients were used to guide the management of places where studies were lacking in paediatric CML. Recently, dasatinib and nilotinib have been approved for treatment of paediatric CML, and their role has been discussed in the current management perspective. Allogeneic transplant, fertility and vaccination in paediatric CML, have also been discussed.

BCR-ABL but not JAK2 V617F inhibits erythropoiesis through the Ras signal by inducing p21CIP1/WAF1

BCR-ABL is a causative tyrosine kinase (TK) of chronic myelogenous leukemia (CML). In CML patients, although myeloid cells are remarkably proliferating, erythroid cells are rather decreased and anemia is commonly observed. This phenotype is quite different from that observed in polycythemia vera (PV) caused by JAK2 V617F, whereas both oncogenic TKs activate common downstream molecules at the level of hematopoietic stem cells (HSCs). To clarify this mechanism, we investigated the effects of BCR-ABL and JAK2 V617F on erythropoiesis. Enforced expression of BCR-ABL but not of JAK2 V617F in murine LSK (Lineage(-)Sca-1(hi)CD117(hi)) cells inhibited the development of erythroid cells. Among several signaling molecules downstream of BCR-ABL, an active mutant of N-Ras (N-RasE12) but not of STAT5 or phosphatidylinositol 3-kinase (PI3-K) inhibited erythropoiesis, while N-RasE12 enhanced the development of myeloid cells. BCR-ABL activated Ras signal more intensely than JAK2 V617F, and inhibition of Ras by manumycin A, a farnesyltransferase inhibitor, ameliorated erythroid colony formation of CML cells. As for the mechanisms of Ras-induced suppression of erythropoiesis, we found that GATA-1, an erythroid-specific transcription factor, blocked Ras-mediated mitogenic signaling at the level of MEK through the direct interaction. Furthermore, enforced expression of N-RasE12 in LSK cells derived from p53-, p16(INK4a)/p19(ARF)-, and p21(CIP1/WAF1)-null/wild-type mice revealed that suppressed erythroid cell growth by N-RasE12 was restored only by p21(CIP1/WAF1) deficiency, indicating that a cyclin-dependent kinase (CDK) inhibitor, p21(CIP1/WAF1), plays crucial roles in Ras-induced suppression of erythropoiesis. These data would, at least partly, explain why respective oncogenic TKs cause different disease phenotypes.

[Chronic myeloid neoplasms. Diagnostic criteria and current therapeutic concepts]

Myeloproliferative neoplasms (MPNs) and related chronic disorders constitute a subgroup of myeloid malignancies which are defined according to clinical, morphological and molecular features by the actual World Health Organization classification of tumors of the haematopietic system. Screening procedures for a BCR-ABL fusion gene, JAK2, thrombopoietin receptor and KIT mutations are formally included in the diagnostic approach. Myelodysplastic/MPN overlap syndromes include rare entities such as refractory anemia with ringed sideroblasts characterized by a high proportion of JAK2V617F mutated cases. The paradigm of targeted treatment of chronic myeloid leukemia with imatinib has now been extended to eosinophilia-associated myeloid neoplasms with PDGFRA, PDGFRB or FGFR1 gene mutations. Pegylated interferon-alpha has convincingly been proved to reduce the JAK2 allele burden. JAK2 inhibitor drugs are currently being tested in clinical trials. The development of pathogenesis-targeted diagnostic and therapeutic approaches to the various MPNs will continue in the future.

Analysis of Risk Factors of the Evolution of Myelofibrosis in Pre-Fibrotic Chronic Idiopathic Myelofibrosis: A retrospective study based on follow up biopsies of 70 patients by using the RECPAM method

The advanced, fibrotic phase of chronic idiopathic myelofibrosis (CIMF) is preceded by a pre-fibrotic stage. However, the factors which may influence or predict the development of myelofibrosis are not well established. Thus we investigated follow up biopsies of 70 patients with CIMF, diagnosed in stages of no or only scant fiber increase, for the development of myelofibrosis. The influence of histopathological (megakaryocytes, initial fiber content), clinical (age, gender, splenomegaly, chemotherapy) and hematological (Hb, leukocyte- and platelet count) parameters on the development of myelofibrosis was evaluated by using the univariate Log Rank method and the multivariate recursive partition and amalgamation (RECPAM) analysis. Surveying a mean observation period of 47 months we found a development of significant myelofibrosis in 30 of the 70 patients. In the univariate analysis, the development of myelofibrosis was associated with increased megakaryocytes, initial fiber content and age of the patient. In the RECPAM analysis, the patients with a high megakaryocytic count and older age showed the highest risk of developing myelofibrosis (mean 58.3 and 60.1 months). The group with the best prognosis comprised the patients under 60 years which have a low content of megakaryocytes (mean 137 months). We found that the development of myelofibrosis in CIMF was best predicted by an increase of megakaryocytes within the bone marrow, possibly reflecting the release of growth factors by these cells. The next important risk factor was the age of the patients.

Chronic myelogenous leukemia, BCR-ABL1+

Session 1 of the 2007 Workshop of the Society for Hematopathology/European Association for Haematopathology focused on chronic myelogenous leukemia, BCR-ABL1+ (CML). CML is a myeloproliferative neoplasm arising at the level of a pluripotent stem cell and consistently associated with the BCR-ABL1 fusion gene. CML most commonly manifests in a chronic phase of the disease with neutrophilic leukocytosis, and the demonstration of the Philadelphia chromosome is the ultimate confirmation of the diagnosis. However, in select cases, the initial diagnosis remains challenging, and a number of issues pertaining to the manifestations and disease evolution remain unresolved. These issues have been illustrated by the cases submitted to our workshop and include unusual manifestations of CML, including manifestation in the accelerated and/or blast phase, and patterns of disease progression and therapy resistance in the era of protein tyrosine kinase inhibitor therapy.

Blast count and cytogenetics correlate and are useful parameters for the evaluation of different phases in chronic myeloid leukemia

Staging of chronic myeloid leukemia (CML) phases is based on cytomorphological criteria that vary considerably between different staging systems. Thus, staging of CML is heterogeneous and causes problems with respect to the comparison of therapeutical strategies and clinical outcome. We evaluated 59 patients with CML in different stages of the disease. In order to define which cytomorphological parameters correlate with cytogenetics we investigated cytomorphology and cytogenetics in parallel in all cases. As a result, bone marrow blast count demonstrated a highly significant correlation with the respective cytogenetic results of the patients and was clearly linked to the frequency and complexity of clonal evolution. We therefore propose to focus staging systems of CML on the correlation of the percentage of bone marrow blasts and the cytogenetic results.

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

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

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

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

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

The incidence of myelofibrosis (MF) among the three major Philadelphia chromosome-negative chronic myeloproliferative disorders, i.e. essential thrombocythaemia (ET), polycythaemia vera (PV) and chronic idiopathic myelofibrosis (CIMF), is not well documented since the diagnostic criteria have recently been redefined by the WHO. Therefore we performed a retrospective analysis of follow-up biopsies of 275 patients with ET, PV and CIMF according to the WHO classification of chronic myeloproliferative disorders. In the diagnostic bone marrow biopsies, MF was observed in 57 of the 136 CIMF patients (42%), 4 of the 73 PV patients (5%) and none of the 66 patients with ET. Within a median observation time of 2.9 years, 34 of the 79 patients with CIMF (43%), 13 of the 69 patients with PV (19%) and 1 of the 66 patients with ET (1.5%)--each initially without MF--developed MF regardless of myelosuppressive therapy.

TGF-beta1 induces bone marrow reticulin fibrosis in hairy cell leukemia

The mechanisms that lead to reticulin fibrosis of bone marrow (BM) in hairy cell leukemia (HCL) are not fully understood. We therefore investigated the involvement of TGF-beta1, a potent fibrogenic cytokine, in this process. Immunoassays revealed that TGF-beta1 is present at higher concentrations in BM, serum, and plasma of HCL patients in comparison with healthy donors (P < 0.001). RT-PCR and immunofluorescence studies showed that TGF-beta1 is overexpressed at the mRNA and protein levels in peripheral blood, spleen, and BM mononuclear cells and that hairy cells (HCs) are the main source of TGF-beta1. Active TGF-beta1 correlated significantly with grades of BM fibrosis, infiltration with HCs, and serum procollagen type III aminoterminal propeptide (PIIINP). Ex vivo studies demonstrated that TGF-beta1 significantly enhances the production and deposition of reticulin and collagen fibers by BM fibroblasts. In addition, BM plasma of HCL patients increased the synthesis of type I and type III procollagens, the main components of reticulin fibers, at the mRNA and protein levels. This fibrogenic activity of BM plasma was abolished by neutralizing anti-TGF-beta1 antibodies. These results show, for the first time to our knowledge, that TGF-beta1 is highly expressed in HCs and is directly involved in the pathogenesis of BM reticulin fibrosis in HCL.

Mixed chimerism of the resident macrophage population after allogeneic bone marrow transplantation for chronic myeloid leukemia

BACKGROUND

Bone marrow macrophages have been recognized to play a crucial role in the functional network that constitutes the microenvironment. In chronic myelogenous leukemia (CML), neoplastic macrophages are presumably responsible for the expansion of the leukemic cell clone. So far, no information is available about a persistence of host-type macrophages after allogeneic bone marrow transplantation (BMT) implicating a lineage-specific mixed chimerism.

METHODS

Bone marrow trephine biopsies were investigated in eight male and five female patients with CML after BMT after a sex-mismatched host/donor constellation. Techniques included immunophenotyping (CD68) for identification of resident macrophages and a simultaneous genotyping with X- and Y-chromosome-specific DNA-probes (fluorescence in situ hybridization). Normal bone marrow and specimens of CML patients before BMT served as controls.

RESULTS

Contrasting an almost 100% congruence with the genotyping in the controls, a mixed chimerism of the CD68+ macrophages and the other host myeloid cells was found. Until 3 months after BMT, incidence of host-type macrophages ranged from 8% to 10%. This feature was also identifiable in the peculiar subset of pseudo-Gaucher cells (PGCs). The number of host-type macrophages failed to decline significantly during the early posttransplant period, because after almost 4 months these were still detectable. On the other hand, in patients showing an initial-to-manifest leukemic relapse, an insidious conversion of up to 50% from the donor to host-type macrophages and myeloid cells occurred.

CONCLUSIONS

The CD68+ resident bone marrow macrophage population including PGCs are involved in the lineage-specific chimerism and minimal residual disease after BMT in CML.

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

PURPOSE

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

PATIENTS AND METHODS

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

RESULTS

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

CONCLUSION

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

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

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

Changing patterns of histological subgroups during therapy of Ph1+ chronic myelogenous leukaemia

AIMS

Bone marrow histopathology reveals a striking heterogeneity at diagnosis of Philadelphia chromosome positive (Ph1+) chronic myelogenous leukaemia (CML). Based on semiquantitative evaluations of the number of megakaryocytes and the content of fibres, various histological subtypes have been postulated. However, little information exists on whether these groups represent stable categories of the different classification systems and whether therapeutic regimes exert any influence on the putative shift of histological patterns.

METHODS AND RESULTS

A retrospective clinicopathological study was performed on 396 bone marrow biopsies derived from 173 patients. There were at least two representative trephines taken at diagnosis and at median intervals of 16 months. Processing of the specimens involved immunostaining with CD61 (megakaryopoiesis) and Ret40f (erythropoiesis) and Gomori's silver impregnation technique. Based on morphometric analysis and in accordance with the general appearance of bone marrow histology three different histological subtypes were distinguished. These consisted of a granulocytic (51 patients), a predominantly megakaryocytic (73 patients) and a myelofibrotic pattern (49 patients). Follow-up biopsies revealed that a significant transition of histological groups occurred and that, independently of treatment modalities, the myelofibrotic category was associated with an unfavourable prognosis. Of the 124 patients without myelofibrosis at onset, 42% later transformed into the myelofibrotic subtype. However, these patients showed no prevalence of either a pre-existing granulocytic or megakaryocytic growth. Myelofibrotic changes were significantly associated with interferon (IFN) and busulfan (BU) therapy. On the other hand, a transition of a myelofibrotic into a nonfibrotic subtype was detectable in 17 of the 49 patients under study and related to hydroxyurea (HU) treatment.

CONCLUSIONS

Histological classification systems of bone marrow features in CML do not represent stable patterns, but may be significantly altered by therapy, in particular IFN and HU.

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

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