Development of monocytosis in patients with primary myelofibrosis indicates an accelerated phase of the disease

Myeloproliferative Neoplasms Transcriptome Reveals Pro-Inflammatory Signature and Enrichment in Peripheral Blood Monocyte-Related Genes

Myeloproliferative neoplasms (MPN) are hematological diseases associated with genetic driver mutations in the JAK2, CALR, and MPL genes and exacerbated oncoinflammatory status. Analyzing public microarray data from polycythemia vera (n = 41), essential thrombocythemia (n = 21), and primary myelofibrosis (n = 9) patients' peripheral blood by in silico approaches, we found that pro-inflammatory and monocyte-related genes were differentially expressed in MPN patients' transcriptome. Genes related to cell activation, secretion of pro-inflammatory and pro-angiogenic mediators, activation of neutrophils and platelets, coagulation, and interferon pathway were upregulated in monocytes compared to controls. Together, our results suggest that molecular alterations in monocytes may contribute to oncoinflammation in MPN.

Real-World Electronic Medical Records Data Identify Risk Factors for Myelofibrosis and Can Be Used to Validate Established Prognostic Scores

Myelofibrosis (MF) is a myeloproliferative neoplasia arising de novo as primary myelofibrosis (PMF) or secondary to polycythemia vera or essential thrombocythemia. Patients experience a high symptom burden and a marked reduction in life expectancy. Despite progress in molecular understanding and treatment, the clinical and prognostic heterogeneity of MF complicates treatment decisions. The International Prognostic Scoring System (IPSS) integrates clinical factors for risk stratification in MF. This study leverages the TriNetX database with more than 64,000 MF patients to assess the impact of accessible parameters on survival and complicating events, including AML transformation, cachexia, increased systemic inflammation, thrombosis and hemorrhage. Age over 65 years correlated with increased risks of death, AML transformation, thrombosis and hemorrhage. Anemia (Hb < 10 g/dL), leukocytosis (>25 × 103/µL) and thrombocytopenia (<150 × 103/µL) reduced survival and increased risks across all assessed events. Monocytosis is associated with decreased survival, whereas eosinophilia and basophilia were linked to improved survival. Further, as proof of concept for the applicability of TriNetX for clinical scores, we devised a simplified IPSS, and confirmed its value in predicting outcomes. This comprehensive study underscores the importance of age, anemia, leukocytosis and thrombocytopenia in predicting disease trajectory and contributes to refining prognostic models, addressing the challenges posed by the disease's heterogeneity.

[Molecular features of 109 patients with chronic myelomonocytic leukemia in a single center]

Objective: To explore the molecular features of chronic myelomonocytic leukemia (CMML) . Methods: According to 2022 World Health Organization (WHO 2022) classification, 113 CMML patients and 840 myelodysplastic syndrome (MDS) patients from March 2016 to October 2021 were reclassified, and the clinical and molecular features of CMML patients were analyzed. Results: Among 113 CMML patients, 23 (20.4%) were re-diagnosed as acute myeloid leukemia (AML), including 18 AML with NPM1 mutation, 3 AML with KMT2A rearrangement, and 2 AML with MECOM rearrangement. The remaining 90 patients met the WHO 2022 CMML criteria. In addition, 19 of 840 (2.3%) MDS patients met the WHO 2022 CMML criteria. At least one gene mutation was detected in 99% of CMML patients, and the median number of mutations was 4. The genes with mutation frequency ≥ 10% were: ASXL1 (48%), NRAS (34%), RUNX1 (33%), TET2 (28%), U2AF1 (23%), SRSF2 (21.1%), SETBP1 (20%), KRAS (17%), CBL (15.6%) and DNMT3A (11%). Paired analysis showed that SRSF2 was frequently co-mutated with ASXL1 (OR=4.129, 95% CI 1.481-11.510, Q=0.007) and TET2 (OR=5.276, 95% CI 1.979-14.065, Q=0.001). SRSF2 and TET2 frequently occurred in elderly (≥60 years) patients with myeloproliferative CMML (MP-CMML). U2AF1 mutations were often mutually exclusive with TET2 (OR=0.174, 95% CI 0.038-0.791, Q=0.024), and were common in younger (<60 years) patients with myelodysplastic CMML (MD-CMML). Compared with patients with absolute monocyte count (AMoC) ≥1×10(9)/L and <1×10(9)/L, the former had a higher median age of onset (60 years old vs 47 years old, P<0.001), white blood cell count (15.9×10(9)/L vs 4.4×10(9)/L, P<0.001), proportion of monocytes (21.5% vs 15%, P=0.001), and hemoglobin level (86 g/L vs 74 g/L, P=0.014). TET2 mutations (P=0.021) and SRSF2 mutations (P=0.011) were more common in patients with AMoC≥1×10(9)/L, whereas U2AF1 mutations (P<0.001) were more common in patients with AMoC<1×10(9)/L. There was no significant difference in the frequency of other gene mutations between the two groups. Conclusion: According to WHO 2022 classification, nearly 20% of CMML patients had AMoC<1×10(9)/L at the time of diagnosis, and MD-CMML and MP-CMML had different molecular features.

Progression in Myeloid Neoplasms: Beyond the Myeloblast

Disease progression in myelodysplastic syndromes (MDS), myelodysplastic-myeloproliferative neoplasms (MDS/MPN), and myeloproliferative neoplasms (MPN), altogether referred to as myeloid neoplasms (MN), is a major source of mortality. Apart from transformation to acute myeloid leukemia, the clinical progression of MN is mostly due to the overgrowth of pre-existing hematopoiesis by the MN without an additional transforming event. Still, MN may evolve along other recurrent yet less well-known scenarios: (1) acquisition of MPN features in MDS or (2) MDS features in MPN, (3) progressive myelofibrosis (MF), (4) acquisition of chronic myelomonocytic leukemia (CMML)-like characteristics in MPN or MDS, (5) development of myeloid sarcoma (MS), (6) lymphoblastic (LB) transformation, (7) histiocytic/dendritic outgrowths. These MN-transformation types exhibit a propensity for extramedullary sites (e.g., skin, lymph nodes, liver), highlighting the importance of lesional biopsies in diagnosis. Gain of distinct mutations/mutational patterns seems to be causative or at least accompanying several of the above-mentioned scenarios. MDS developing MPN features often acquire MPN driver mutations (usually JAK2), and MF. Conversely, MPN gaining MDS features develop, e.g., ASXL1, IDH1/2, SF3B1, and/or SRSF2 mutations. Mutations of RAS-genes are often detected in CMML-like MPN progression. MS ex MN is characterized by complex karyotypes, FLT3 and/or NPM1 mutations, and often monoblastic phenotype. MN with LB transformation is associated with secondary genetic events linked to lineage reprogramming leading to the deregulation of ETV6, IKZF1, PAX5, PU.1, and RUNX1. Finally, the acquisition of MAPK-pathway gene mutations may shape MN toward histiocytic differentiation. Awareness of all these less well-known MN-progression types is important to guide optimal individual patient management.

Cytological Diagnosis of Classic Myeloproliferative Neoplasms at the Age of Molecular Biology

Myeloproliferative neoplasms (MPN) are clonal hematopoietic stem cell-derived disorders characterized by uncontrolled proliferation of differentiated myeloid cells. Two main groups of MPN, BCR::ABL1-positive (Chronic Myeloid Leukemia) and BCR::ABL1-negative (Polycythemia Vera, Essential Thrombocytosis, Primary Myelofibrosis) are distinguished. For many years, cytomorphologic and histologic features were the only proof of MPN and attempted to distinguish the different entities of the subgroup BCR::ABL1-negative MPN. World Health Organization (WHO) classification of myeloid neoplasms evolves over the years and increasingly considers molecular abnormalities to prove the clonal hematopoiesis. In addition to morphological clues, the detection of JAK2, MPL and CALR mutations are considered driver events belonging to the major diagnostic criteria of BCR::ABL1-negative MPN. This highlights the preponderant place of molecular features in the MPN diagnosis. Moreover, the advent of next-generation sequencing (NGS) allowed the identification of additional somatic mutations involved in clonal hematopoiesis and playing a role in the prognosis of MPN. Nowadays, careful cytomorphology and molecular biology are inseparable and complementary to provide a specific diagnosis and to permit the best follow-up of these diseases.

Advances in myelodysplastic/myeloproliferative neoplasms

The myelodysplastic syndrome/myeloproliferative neoplasms (MDS/MPN) category includes a heterogeneous group of diseases characterized by the co-occurrence of clinical and pathologic features of both myelodysplastic and myeloproliferative neoplasms. The recently published International Consensus Classification of myeloid neoplasms revised the entities included in the MDS/MPN category as well as criteria for their diagnosis. In addition to the presence of one or more increased peripheral blood cell counts as evidence of myeloproliferative features, concomitant cytopenia as evidence of ineffective hematopoiesis is now an explicit requirement to diagnose the diseases included in this category. The increasing availability of modern gene sequencing has allowed better understanding of the biologic characteristics of these myeloid neoplasms. The presence of specific mutations in the appropriate clinicopathologic context is now included in the diagnostic criteria for some of MDS/MPN entities. In this review, we highlight what has changed in the diagnostic criteria of MDS/MPN from the WHO 2016 classification while providing practical guidance in diagnosing these diseases.

Philadelphia-negative myeloproliferative neoplasms display alterations in monocyte subpopulations frequency and immunophenotype

Philadelphia-negative myeloproliferative neoplasms (MPN) are clonal hematological diseases associated with driver mutations in JAK2, CALR, and MPL genes. Moreover, several evidence suggests that chronic inflammation and alterations in stromal and immune cells may contribute to MPN’s pathophysiology. We evaluated the frequency and the immunophenotype of peripheral blood monocyte subpopulations in patients with polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (MF). Peripheral blood monocytes from PV (n = 16), ET (n = 16), and MF (n = 15) patients and healthy donors (n = 10) were isolated and submitted to immunophenotyping to determine the frequency of monocyte subpopulations and surface markers expression density. Plasma samples were used to measure the levels of soluble CD163, a biomarker of monocyte activity. PV, ET, and MF patients presented increased frequency of intermediate and non-classical monocytes and reduced frequency of classical monocytes compared to controls. Positivity for JAK2 mutation was significantly associated with the percentage of intermediate monocytes. PV, ET, and MF patients presented high-activated monocytes, evidenced by higher HLA-DR expression and increased soluble CD163 levels. The three MPN categories presented increased frequency of CD56⁺ aberrant monocytes, and PV and ET patients presented reduced frequency of CD80/86⁺ monocytes. Therefore, alterations in monocyte subpopulations frequency and surface markers expression pattern may contribute to oncoinflammation and may be associated with the pathophysiology of MPN.

The ABNL-MARRO 001 study: a phase 1-2 study of randomly allocated active myeloid target compound combinations in MDS/MPN overlap syndromes

BACKGROUND

Myelodysplastic/myeloproliferative neoplasms (MDS/MPN) comprise several rare hematologic malignancies with shared concomitant dysplastic and proliferative clinicopathologic features of bone marrow failure and propensity of acute leukemic transformation, and have significant impact on patient quality of life. The only approved disease-modifying therapies for any of the MDS/MPN are DNA methyltransferase inhibitors (DNMTi) for patients with dysplastic CMML, and still, outcomes are generally poor, making this an important area of unmet clinical need. Due to both the rarity and the heterogeneous nature of MDS/MPN, they have been challenging to study in dedicated prospective studies. Thus, refining first-line treatment strategies has been difficult, and optimal salvage treatments following DNMTi failure have also not been rigorously studied. ABNL-MARRO (A Basket study of Novel therapy for untreated MDS/MPN and Relapsed/Refractory Overlap Syndromes) is an international cooperation that leverages the expertise of the MDS/MPN International Working Group (IWG) and provides the framework for collaborative studies to advance treatment of MDS/MPN and to explore clinical and pathologic markers of disease severity, prognosis, and treatment response.

METHODS

ABNL MARRO 001 (AM-001) is an open label, randomly allocated phase 1/2 study that will test novel treatment combinations in MDS/MPNs, beginning with the novel targeted agent itacitinib, a selective JAK1 inhibitor, combined with ASTX727, a fixed dose oral combination of the DNMTi decitabine and the cytidine deaminase inhibitor cedazuridine to improve decitabine bioavailability.

DISCUSSION

Beyond the primary objectives of the study to evaluate the safety and efficacy of novel treatment combinations in MDS/MPN, the study will (i) Establish the ABNL MARRO infrastructure for future prospective studies, (ii) Forge innovative scientific research that will improve our understanding of pathogenetic mechanisms of disease, and (iii) Inform the clinical application of diagnostic criteria, risk stratification and prognostication tools, as well as response assessments in this heterogeneous patient population.

TRIAL REGISTRATION

This trial was registered with ClinicalTrials.gov on August 19, 2019 (Registration No. NCT04061421).

International Consensus Classification of Myeloid Neoplasms and Acute Leukemias: integrating morphologic, clinical, and genomic data

The classification of myeloid neoplasms and acute leukemias was last updated in 2016 within a collaboration between the World Health Organization (WHO), the Society for Hematopathology, and the European Association for Haematopathology. This collaboration was primarily based on input from a clinical advisory committees (CACs) composed of pathologists, hematologists, oncologists, geneticists, and bioinformaticians from around the world. The recent advances in our understanding of the biology of hematologic malignancies, the experience with the use of the 2016 WHO classification in clinical practice, and the results of clinical trials have indicated the need for further revising and updating the classification. As a continuation of this CAC-based process, the authors, a group with expertise in the clinical, pathologic, and genetic aspects of these disorders, developed the International Consensus Classification (ICC) of myeloid neoplasms and acute leukemias. Using a multiparameter approach, the main objective of the consensus process was the definition of real disease entities, including the introduction of new entities and refined criteria for existing diagnostic categories, based on accumulated data. The ICC is aimed at facilitating diagnosis and prognostication of these neoplasms, improving treatment of affected patients, and allowing the design of innovative clinical trials.

Myeloproliferative Neoplasms with Monocytosis

PURPOSE OF REVIEW

Myeloproliferative neoplasms (MPN) are a heterogeneous group of hematopoietic stem cell neoplasms comprising of polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF) that share driver mutations (JAK2/CALR/MPL) resulting in constitutive activation of JAK/STAT and other signaling pathways. Patients with MPN have shortened survival and an inherent risk for leukemic evolution. Prognostically relevant clinical and genetic parameters have been incorporated into mutation-enhanced scoring systems (MIPSS70-plus version 2.0, MIPSS-ET/PV). In the current review, we describe clinical and pathological features along with prognostic significance of MPN with monocytosis.

RECENT FINDINGS

Monocytosis, defined by an absolute monocyte count (AMC) ≥ 1 × 10 ⁹/L, is a typical manifestation of chronic myelomonocytic leukemia (CMML) but is also associated with 21% and 17% of PV and PMF patients, respectively. Recent studies on the subject have reported that MPN patients with monocytosis are older and present with concomitant leukocytosis. In regard to PV, patients with monocytosis harbor unfavorable cytogenetic abnormalities including +8, 7/7q, i(17q), 5/5q-,12p-, inv(3), or 11q23 rearrangement and SRSF2 mutations, whereas PMF patients with monocytosis had significant thrombocytopenia, higher circulating blasts, higher symptom burden, and ASXL1 mutations. Moreover, presence of monocytosis predicted inferior survival in both PV and PMF. Monocytosis in MPN is associated with a distinct clinical and genetic profile and may serve as a marker of aggressive disease biology.

The Classification of Myeloproliferative Neoplasms: Rationale, Historical Background and Future Perspectives with Focus on Unclassifiable Cases

Myeloproliferative neoplasms (MPNs) are a heterogeneous group of clonal hematopoietic stem cell disorders, characterized by increased proliferation of one or more myeloid lineages in the bone marrow. The classification and diagnostic criteria of MPNs have undergone relevant changes over the years, reflecting the increased awareness on these conditions and a better understanding of their biological and clinical-pathological features. The current World Health Organization (WHO) Classification acknowledges four main sub-groups of MPNs: (i) Chronic Myeloid Leukemia; (ii) classical Philadelphia-negative MPNs (Polycythemia Vera; Essential Thrombocythemia; Primary Myelofibrosis); (iii) non-classical Philadelphia-negative MPNs (Chronic Neutrophilic Leukemia; Chronic Eosinophilic Leukemia); and (iv) MPNs, unclassifiable (MPN-U). The latter are currently defined as MPNs with clinical-pathological findings not fulfilling the diagnostic criteria for any other entity. The MPN-U spectrum traditionally encompasses early phase MPNs, terminal (i.e., advanced fibrotic) MPNs, and cases associated with inflammatory or neoplastic disorders that obscure the clinical-histological picture. Several lines of evidence and clinical practice suggest the existence of additional myeloid neoplasms that may expand the spectrum of MPN-U. To gain insight into such disorders, this review addresses the history of MPN classification, the evolution of their diagnostic criteria and the complex clinical-pathological and biological features of MPN-U.

Progression in Ph-Chromosome-Negative Myeloproliferative Neoplasms: An Overview on Pathologic Issues and Molecular Determinants

Progression in Ph-chromosome-negative myeloproliferative neoplasms (MPN) develops with variable incidence and time sequence in essential thrombocythemia, polycythemia vera, and primary myelofibrosis. These diseases show different clinic-pathologic features and outcomes despite sharing deregulated JAK/STAT signaling due to mutations in either the Janus kinase 2 or myeloproliferative leukemia or CALReticulin genes, which are the primary drivers of the diseases, as well as defined diagnostic criteria and biomarkers in most cases. Progression is defined by the development or worsening of marrow fibrosis or the progressive increase in the marrow blast percentage. Progression is often related to additional genetic aberrations, although some can already be detected during the chronic phase. Detailed scoring systems for clinical usage that are mostly applied in patients with primary myelofibrosis have been defined, and the most recent ones include cytogenetic and molecular parameters with prognostic significance. Additional different clinic-pathologic changes have been reported that may occur during the course of the disease and that are, at present, classified as WHO-defined types of progression, although they likely represent such an event. The present review is meant to provide an updated overview on progression in Ph-chromosome-negative MPN, with a major focus on the pathologic side.

Progression in Ph-Chromosome-Negative Myeloproliferative Neoplasms: An Overview on Pathologic Issues and Molecular Determinants

Progression in Ph-chromosome-negative myeloproliferative neoplasms (MPN) develops with variable incidence and time sequence in essential thrombocythemia, polycythemia vera, and primary myelofibrosis. These diseases show different clinic-pathologic features and outcomes despite sharing deregulated JAK/STAT signaling due to mutations in either the Janus kinase 2 or myeloproliferative leukemia or CALReticulin genes, which are the primary drivers of the diseases, as well as defined diagnostic criteria and biomarkers in most cases. Progression is defined by the development or worsening of marrow fibrosis or the progressive increase in the marrow blast percentage. Progression is often related to additional genetic aberrations, although some can already be detected during the chronic phase. Detailed scoring systems for clinical usage that are mostly applied in patients with primary myelofibrosis have been defined, and the most recent ones include cytogenetic and molecular parameters with prognostic significance. Additional different clinic-pathologic changes have been reported that may occur during the course of the disease and that are, at present, classified as WHO-defined types of progression, although they likely represent such an event. The present review is meant to provide an updated overview on progression in Ph-chromosome-negative MPN, with a major focus on the pathologic side.

Altered T-cell subset repertoire affects treatment outcome of patients with myelofibrosis

Phenotypic characterization of T cells in myelofibrosis is intriguing because of increased inflammation, markedly elevated pro-inflammatory cytokines, and altered distribution of T-cell subsets. Constitutive activation of Janus kinase-2 (JAK2) in the majority of patients with myelofibrosis contributes to the expression of the programmed cell death protein-1 (PD1) and T-cell exhaustion. We wondered whether T-cell activation affects treatment outcome of patients with myelofibrosis and sought to determine whether the JAK1/2 inhibitor ruxolitinib affects the activation of T-cell subsets. T cells from 47 myelofibrosis patients were analyzed and the percentages of either helper (CD4+) or cytotoxic (CD8+) naïve, central memory, effector memory, or effector T cells; and fractions of PD1-expressing cells in each subset were assessed. Higher numbers of T cells co-expressing CD4/PD1 and CD8/PD1 were found in myelofibrosis patients than in healthy controls (n=28), and the T cells were significantly skewed toward an effector phenotype in both CD4+ and CD8+ subsets, consistent with a shift from a quiescent to an activated state. Over the course of ruxolitinib treatment, the distribution of aberrant T-cell subsets significantly reversed towards resting cell phenotypes. CD4+ and CD8+ subsets at baseline correlated with monocyte and platelet counts, and their PD1+ fractions correlated with leukocyte counts and spleen size. Low numbers of PD1+/CD4+ and PD1+/CD8+ cells were associated with complete resolution of palpable splenomegaly and improved survival rate, suggesting that low levels of exhausted T cells confer a favorable response to ruxolitinib treatment.

Clinical and Laboratory Features of JAK2 V617F, CALR, and MPL Mutations in Malaysian Patients with Classical Myeloproliferative Neoplasm (MPN)

Mutations of JAK2V617F, CALR, and MPL genes confirm the diagnosis of myeloproliferative neoplasm (MPN). This study aims to determine the genetic profile of JAK2V617F, CALR exon 9 Type 1 (52 bp deletion) and Type 2 (5 bp insertion), and MPL W515 L/K genes among Malaysian patients and correlate these mutations with clinical and hematologic parameters in MPN. Mutations of JAK2V617F, CALR, and MPL were analyzed in 159 Malaysian patients using allele-specific polymerase chain reaction, including 76 polycythemia vera (PV), 41 essential thrombocythemia (ET), and 42 primary myelofibrosis (PMF) mutations, and the demographics of the patients were retrieved. The result showed that 73.6% JAK2V617F, 5.66% CALR, and 27.7% were triple-negative mutations. No MPL W515L/K mutation was detected. In ET and PMF, the predominance type was the CALR Type 1 mutation. In JAK2V617F mutant patients, serum LDH was significantly higher in PMF compared to PV and ET. PV has a higher risk of evolving to post PV myelofibrosis compared to ET. A thrombotic event at initial diagnosis of 40.9% was high compared to global incidence. Only one PMF patient had a CALR mutation that transformed to acute myeloid leukemia. JAK2V617F and CALR mutations play an important role in diagnostics. Hence, every patient suspected of having a myeloproliferative neoplasm should be screened for these mutations.

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.

Laboratory Evaluation and Pathological Workup of Neoplastic Monocytosis - Chronic Myelomonocytic Leukemia and Beyond

PURPOSE OF REVIEW

Monocytosis is a distinct but non-specific manifestation of various physiologic and pathologic conditions. Among hematopoietic stem cell neoplasms, depending on the criteria used for disease classification, monocytosis may be a consistent and integral component of diseases such as chronic myelomonocytic leukemia or acute myeloid leukemia with monocytic differentiation, or it may represent an inconsistent finding that often provides a clue to the underlying genetic changes driving the neoplasm. The purpose of this review is to provide the readers with a laboratory-based approach to neoplastic monocytosis.

RECENT FINDINGS

In-depth elucidation of the genomic landscape of myeloid neoplasms within the past few years has broadened our understanding of monocytosis and its implications for diagnosis and prognosis. Genetic findings also shed light on potential disease response - or lack thereof - to various therapeutic agents used in the setting of myeloid neoplasms. In this review, we provide our approach to diagnose neoplastic monocytosis in the context of case-based studies while incorporating the most recent literature on this topic.

Contemporary Risk Stratification and Treatment of Chronic Myelomonocytic Leukemia

Chronic myelomonocytic leukemia (CMML) is a hematologic malignancy characterized by absolute monocytosis, one or more lineage dysplasia, and proliferative features including myeloid hyperplasia, splenomegaly, and constitutional symptoms. Because of vast clinical heterogeneity in presentation and course, risk stratification is used for a risk-adapted treatment strategy. Numerous prognostic scoring systems exist, some of which incorporate mutational information. Treatment ranges from observation to allogeneic hematopoietic stem cell transplantation. Therapies include hydroxyurea for cytoreduction, hypomethylating agents, and the JAK1/2 inhibitor ruxolitinib to address splenomegaly and constitutional symptoms. Recently, oral decitabine with cedazuridine was approved and represents a convenient treatment option for CMML patients. Although novel therapeutics are in development for CMML, further work is needed to elucidate possible targets unique to the CMML clone. In this review, we will detail the pathophysiology, risk stratification, available treatment modalities, and novel therapies for CMML, and propose a modern treatment algorithm. IMPLICATIONS FOR PRACTICE: Chronic myelomonocytic leukemia (CMML) is a clinically heterogenous disease, which poses significant management challenges. The diagnosis of CMML requires bone marrow biopsy and aspirate with thorough evaluation. Risk stratification and symptom assessment are essential to designing an effective treatment plan, which may include hypomethylating agents (HMAs) in intermediate or high-risk patients. The recently approved oral decitabine/cedazuridine provides a convenient alternative to parenteral HMAs. Ruxolitinib may be effective in ameliorating proliferative symptoms and splenomegaly. Allogeneic stem cell transplantation remains the only treatment with curative potential; however, novel therapies are in clinical development which may significantly alter the therapeutic landscape of CMML.

Clinical and Molecular Approach to Adult-Onset, Neoplastic Monocytosis

PURPOSE OF REVIEW

In this review, we provide a comprehensive and contemporary understanding of malignant monocytosis and provide a framework by which the appropriate diagnosis with malignant monocytosis can be rendered.

RECENT FINDINGS

Increasing data support the use of molecular data to refine the diagnostic approach to persistent monocytosis. The absence of a TET2, SRSF2, or ASXL1 mutation has ≥ 90% negative predictive value for a diagnosis of CMML. These data may also reliably differentiate chronic myelomonocytic leukemia, the malignancy that is most associated with mature monocytosis, from several other diseases that can be associated with typically a lesser degree of monocytosis. These include acute myelomonocytic leukemia, acute myeloid leukemia with monocytic differentiation, myelodysplastic syndromes, and myeloproliferative neoplasms driven by BCR-ABL1, PDGFRA, PDGFRB, or FGFR1 rearrangements or PCM1-JAK2 fusions among other rarer aberrations. The combination of monocyte partitioning with molecular data in patients with persistent monocytosis may increase the predictive power for the ultimate development of CMM but has not been prospectively validated. Many conditions, both benign and malignant, can be associated with an increase in mature circulating monocytes. After reasonably excluding a secondary or reactive monocytosis, there should be a concern for and investigation of malignant monocytosis, which includes hematopathologic review of blood and marrow tissues, flow cytometric analysis, and cytogenetic and molecular studies to arrive at an appropriate diagnosis.

Accelerated Phase of Myeloproliferative Neoplasms

BACKGROUND

Myeloproliferative neoplasms (MPNs) can transform into blast phase MPN (leukemic transformation; MPN-BP), typically via accelerated phase MPN (MPN-AP), in ∼20-25% of the cases. MPN-AP and MPN-BP are characterized by 10-19% and ≥20% blasts, respectively. MPN-AP/BP portend a dismal prognosis with no established conventional treatment. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the sole modality associated with long-term survival.

SUMMARY

MPN-AP/BP has a markedly different mutational profile from de novo acute myeloid leukemia (AML). In MPN-AP/BP, TP53 and IDH1/2 are more frequent, whereas FLT3 and DNMT3A are rare. Higher incidence of leukemic transformation has been associated with the most aggressive MPN subtype, myelofibrosis (MF); other risk factors for leukemic transformation include rising blast counts above 3-5%, advanced age, severe anemia, thrombocytopenia, leukocytosis, increasing bone marrow fibrosis, type 1 CALR-unmutated status, lack of driver mutations (negative for JAK2, CALR, or MPL genes), adverse cytogenetics, and acquisition of ≥2 high-molecular risk mutations (ASXL1, EZH2, IDH1/2, SRSF2, and U2AF1Q157). The aforementioned factors have been incorporated in several novel prognostic scoring systems for MF. Currently, elderly/unfit patients with MPN-AP/BP are treated with hypomethylating agents with/without ruxolitinib; these regimens appear to confer comparable benefit to intensive chemotherapy but with lower toxicity. Retrospective studies in patients who acquired actionable mutations during MPN-AP/BP showed positive outcomes with targeted AML treatments, such as IDH1/2 inhibitors, and require further evaluation in clinical trials. Key Messages: Therapy for MPN-AP patients represents an unmet medical need. MF patients, in particular, should be appropriately stratified regarding their prognosis and the risk for transformation. Higher-risk patients should be monitored regularly and treated prior to progression to MPN-BP. MPN-AP patients may be treated with hypomethylating agents alone or in combination with ruxolitinib; also, patients can be provided with the option to enroll in rationally designed clinical trials exploring combination regimens, including novel targeted drugs, with an ultimate goal to transition to transplant.

Eosinophilia/Hypereosinophilia in the Setting of Reactive and Idiopathic Causes, Well-Defined Myeloid or Lymphoid Leukemias, or Germline Disorders

OBJECTIVES

To report the findings of the 2019 Society for Hematopathology/European Association for Haematopathology Workshop within the categories of reactive eosinophilia, hypereosinophilic syndrome (HES), germline disorders with eosinophilia (GDE), and myeloid and lymphoid neoplasms associated with eosinophilia (excluding entities covered by other studies in this series).

METHODS

The workshop panel reviewed 109 cases, assigned consensus diagnosis, and created diagnosis-specific sessions.

RESULTS

The most frequent diagnosis was reactive eosinophilia (35), followed by acute leukemia (24). Myeloproliferative neoplasms (MPNs) received 17 submissions, including chronic eosinophilic leukemia, not otherwise specified (CEL, NOS). Myelodysplastic syndrome (MDS), MDS/MPN, and therapy-related myeloid neoplasms received 11, while GDE and HES received 12 and 11 submissions, respectively.

CONCLUSIONS

Hypereosinophilia and HES are defined by specific clinical and laboratory criteria. Eosinophilia is commonly reactive. An acute leukemic onset with eosinophilia may suggest core-binding factor acute myeloid leukemia, blast phase of chronic myeloid leukemia, BCR-ABL1-positive leukemia, or t(5;14) B-lymphoblastic leukemia. Eosinophilia is rare in MDS but common in MDS/MPN. CEL, NOS is a clinically aggressive MPN with eosinophilia as the dominant feature. Bone marrow morphology and cytogenetic and/or molecular clonality may distinguish CEL from HES. Molecular testing helps to better subclassify myeloid neoplasms with eosinophilia and to identify patients for targeted treatments.

Progression, transformation, and unusual manifestations of myelodysplastic syndromes and myelodysplastic-myeloproliferative neoplasms: lessons learned from the XIV European Bone Marrow Working Group Course 2019

Disease progression in myelodysplastic syndromes (MDS) and myelodysplastic-myeloproliferative neoplasms (MDS/MPN) is a major source of mortality. The European Bone Marrow Working Group organized a dedicated workshop to address MDS and MDS/MPN progression, and myeloid neoplasms with histiocytic and lymphoblastic outgrowths in 2019 in Frankfurt, Germany. In this report, we summarize clinical, histopathological, and molecular features of 28 cases. Most cases illustrate that prognostic mutational profiles change during follow-up due to accumulation of high-risk mutations in the trunk clone, and that results from repeated molecular testing can often explain the clinical progression, suggesting that regular genetic testing may predict transformation by early detection of aggressive clones. Importantly, identical mutations can be linked to different clinical behaviors or risks of fibrotic progression and/or transformation in a context-dependent manner, i.e., MDS or MDS/MPN. Moreover, the order of mutational acquisition and the involved cell lineages matter. Several cases exemplify that histiocytic outgrowths in myeloid neoplasms are usually accompanied by a more aggressive clinical course and may be considered harbinger of disease progression. Exceptionally, lymphoblastic transformations can be seen. As best estimable, the histiocytic and lymphoblastic compounds in all occasions were clonally related to the myeloid compound and-where studied-displayed genomic alterations of, e.g., transcription factor genes or genes involved in MAPK signaling that might be mechanistically linked to the respective type of non-myeloid outgrowth.

Clinical, Hematologic, Biologic and Molecular Characteristics of Patients with Myeloproliferative Neoplasms and a Chronic Myelomonocytic Leukemia-Like Phenotype

Patients with a myeloproliferative neoplasm (MPN) sometimes show a chronic myelomonocytic leukemia (CMML)-like phenotype but, according to the 2016 WHO classification, a documented history of an MPN excludes the diagnosis of CMML. Forty-one patients with an MPN (35 polycythemia vera (PV), 5 primary myelofibrosis, 1 essential thrombocythemia) and a CMML-like phenotype (MPN/CMML) were comprehensively characterized regarding clinical, hematologic, biologic and molecular features. The white blood cell counts in MPN/CMML patients were not different from CMML patients and PV patients. The hemoglobin values and platelet counts of these patients were higher than in CMML but lower than in PV, respectively. MPN/CMML patients showed myelomonocytic skewing, a typical in vitro feature of CMML but not of PV. The mutational landscape of MPN/CMML was not different from JAK2-mutated CMML. In two MPN/CMML patients, development of a CMML-like phenotype was associated with a decrease in the JAK2 V617F allelic burden. Finally, the prognosis of MPN/CMML (median overall survival (OS) 27 months) was more similar to CMML (JAK2-mutated, 28 months; JAK2-nonmutated 29 months) than to PV (186 months). In conclusion, we show that patients with MPN and a CMML-like phenotype share more characteristics with CMML than with PV, which may be relevant for their classification and clinical management.

How I investigate chronic myelomonocytic leukemia

The 2016 revised 4th edition of the World Health Organization classification of hematopoietic neoplasms updated the diagnostic criteria for chronic myelomonocytic leukemia (CMML). Persistent peripheral blood monocytosis of at least 1 × 10⁹ /L and a percentage of monocytes ≥10% of the circulating white blood cell count (WBC) are both prerequisite criteria for this diagnosis. CMML represents the prototype of "overlapping" myeloid neoplasms with concurrent myeloproliferative and myelodysplastic features. However, clinical presentation is heterogeneous, with cases showing prevailing "dysplastic" features and others a predominant "proliferative" phenotype. Accounting for this diversity, two variants of CMML are recognized: "dysplastic" CMML defined by WBC < 13 × 10⁹ /L and "proliferative" CMML with WBC ≥ 13 × 10⁹ /L often showing features mimicking a myeloproliferative neoplasm. Although not an official WHO category, the "oligomonocytic" variant of CMML is defined by relative monocytosis with an absolute monocyte count of 0.5-0.9 × 10⁹ /L. It can be considered a "pre-phase," as it frequently anticipates the development of an overt, classic CMML. In an attempt at improving disease prognostication, the blast count based grading system for CMML of the WHO 2008 Classification has been expanded in 2016 to include a new "CMML-0" category. Lastly, the large body of knowledge on the molecular events occurring in CMML has been used to assist diagnosis and assess prognosis. Despite the step forwards, diagnosis of CMML still remains one of exclusion as no clinical, pathologic or molecular findings are specific for this disease. The current review brings insight into the spectrum of CMML and provides practical advice to approach suspected cases of CMML.

Treatment of MDS/MPN and the MDS/MPN IWG International Trial: ABNL MARRO

PURPOSE OF REVIEW

MDS/MPNs comprise a group of rare hematologic malignancies that balance features of myeloproliferation and bone marrow failure. Given overlapping clinical features and rarity of incidence, MDS/MPNs have long posed a diagnostic and therapeutic challenge. Herein, we sought to review recent advances in diagnosis and emerging therapeutic strategies and highlight the upcoming ABNL MARRO study which aims to individualize therapy for patients with MDS/MPN.

RECENT FINDINGS

Focused study of molecular mutations in MDS/MPNs has provided improved diagnostic clarity. Specific gene mutation or patterns of mutation have been increasingly described and have helped to distinguish between clinically similar diseases. While the current treatment landscape consists largely of therapies that have been co-opted from related disease, the emergence of prospective clinical trials specifically focused on MDS/MPN and the increased use of targeted agents represent progress for patients with MDS/MPN. An improved understanding of the molecular drivers of myeloid diseases has provided diagnostic clarity and renewed hope of targeted therapies for MDS/MPN patients. The upcoming ABNL MARRO study hopes to leverage this knowledge to match patients with targeted therapeutic options specific to molecular drivers of their disease.

Advances in potential treatment options for myeloproliferative neoplasm associated myelofibrosis

INTRODUCTION

The Janus kinase (JAK)1/2 inhibitor ruxolitinib provides rapid, sustained and often dramatic benefits to patients with myelofibrosis, inducing spleen shrinkage and ameliorating symptoms, and improves survival. However, the drug has little effect on the underlying bone marrow fibrosis or on mutant allele burden, and clinical resistance eventually develops. Furthermore, ruxolitinib-induced cytopenias can be challenging in everyday practice.

AREAS COVERED

The developmental therapeutics landscape in MF is discussed. This includes potential partners for ruxolitinib being developed with an aim to improve cytopenias, or to enhance its disease-modifying effects. The development of other JAK inhibitors with efficacy post-ruxolitinib or other unique attributes is being pursued in earnest. Agents with novel mechanisms of action are being studied in patients whose disease responds sub-optimally to, is refractory to or progresses after ruxolitinib.

EXPERT OPINION

The JAK inhibitors fedratinib, pacritinib and momelotinib are clearly active, and it is expected that one or more of these will become licensed in the future. The activin receptor ligand traps are promising as treatments for anemia. Imetelstat has shown interesting activity post-ruxolitinib, and azactidine may be a useful partner for ruxolitinib in some patients. Appropriately, multiple pre-clinical and clinical leads are being pursued in this difficult therapeutic area.

Persistent Basophilia May Suggest an "Accelerated Phase" in the Evolution of CALR-Positive Primary Myelofibrosis Toward Acute Myeloid Leukemia

Basophils are white blood cells that play an important role in the human immune system. These cells physiologically increase in number in immune response to certain allergies, chronic inflammation, and parasitic infections. Basophils are also a significant indicator for the presence of certain malignancies such as chronic myeloproliferative neoplasms and acute myeloid leukemia. In the current manuscript we present a statistically significant correlation between persistent basophilia in primary myelofibrosis (PMF) and the risk for the subsequent development of acute myeloid leukemia. We have retrospectively identified in the files of the Department of Hematology, Ion Chiricuta Clinical Cancer Center in Cluj Napoca, Romania 623 consecutive patients diagnosed with AML over a period spanning from 2008 to 2018. We afterwards identified 32 patients with AML diagnosis following a previous diagnosis of myelofibrosis (either post-PV, post-ET, or post-PMF). All the patients were diagnosed according to the WHO criteria. We subsequently established a control group consisting of 32 patients with underlying BCR-ABL-negative MPN who did not develop AML (AML-negative group). Following this, we assessed whether the AML-negative patients from our control group also had a persistent (>3 months) absolute basophilia. When comparing both groups of patients with myelofibrosis, the group with subsequent AML development and the one without AML, the follow-up did not present statistically significant differences between the two groups. In the univariate analysis, patients who progressed to AML had more frequently basophilia, longer basophilia duration, higher pre-therapy absolute, and relative basophil count and presented more frequently calreticulin (CALR) mutations. In the current study, we emphasize the need for a closer clinical monitoring for chronic MPNs with marked basophilia, with an important potential clinical impact.

Genetic Testing in the Diagnosis and Biology of Myeloid Neoplasms (Excluding Acute Leukemias)

OBJECTIVES

The 2017 Workshop of the Society for Hematopathology/European Association for Haematopathology reviewed the role of genetic testing in the diagnosis of hematopoietic neoplasms, including non-acute leukemia myeloid malignancies.

METHODS

The workshop panel assigned 98 submitted cases to the category of non-acute leukemia myeloid neoplasms, of which 13 were selected for oral presentation.

RESULTS

Data from both conventional karyotyping and genetic sequencing had important impact on diagnosis, classification, and prognostication. However, some cases had genetic results that appeared discordant from the morphology and/or clinical features. Thus, the workshop underscored the need for careful management of genetic data by the pathologist and clinician, in the context of other findings.

CONCLUSIONS

The workshop cases highlighted the significance of genetic aberrations in the diagnosis and treatment of non-acute leukemia myeloid neoplasms. Many genetic data have already been incorporated in the most recent World Health Organization classification, and undoubtedly they will factor increasingly in future classifications.

Chronic Myelomonocytic Leukemia With Fibrosis Is a Distinct Disease Subset With Myeloproliferative Features and Frequent JAK2 p.V617F Mutations

A subset of patients with chronic myelomonocytic leukemia (CMML) presents with significance myelofibrosis. In myelodysplastic syndromes, significant myelofibrosis has been associated with adverse outcomes and p53 dysregulation. However, in CMML the clinical and molecular correlates of significant myelofibrosis at presentation remain poorly understood. From a cohort of 651 CMML patients, we identified retrospectively 20 (3.1%) cases with moderate to severe reticulin fibrosis (CMML-F) detected at diagnosis, and we compared them to CMML patients without fibrosis (n=631) seen during the same period. Patients with CMML-F had a median age of 69.8 years (range, 24.8 to 91.2 y) and most (13; 65%) were men. Patients with CMML-F differed significantly from other CMML patients across the following parameters: white blood count, absolute monocyte count, serum lactate dehydrogenase level, splenomegaly, and bone marrow blast percentage. Notably, the frequency of JAK2 p.V617F mutation was higher in CMML-F patients compared with other CMML patients (P<0.001). Most CMML-F patients (12/20; 60%) had myeloproliferative CMML. Dysregulation of p53 was uncommon in CMML-F. CMML-F patients tended to have a shorter median overall survival compared with other CMML patients (P=0.079). Multivariate analysis using the Cox proportional hazards model showed an independent association between CMML-F and overall survival (P=0.047). In summary, unlike typical CMML, CMML-F is commonly associated with JAK2 p.V617F. The high frequency of myeloproliferative features and JAK2 p.V617F mutation, and the low frequency of p53 dysregulation, suggest that fibrosis in the context of CMML has a different pathogenesis from that previously reported in myelodysplastic syndrome.

Update on the pathologic diagnosis of chronic myelomonocytic leukemia

The diagnostic criteria for chronic myelomonocytic leukemia were recently revised in the 2016 World Health Organization classification update and include new and revised subtypes. In addition, molecular genetic studies have provided new insights into the prognosis and diagnosis of this myeloid neoplasm. This review summarizes the 2016 changes to the diagnostic criteria, discusses potential future changes that may impact diagnosis and provides an overview of recent advances in the diagnosis and prognosis determination of chronic myelomonocytic leukemia.

Blast Transformation in Myeloproliferative Neoplasms: Risk Factors, Biological Findings, and Targeted Therapeutic Options

Myeloproliferative neoplasms represent a heterogenous group of disorders of the hematopoietic stem cell, with an intrinsic risk of evolution into acute myeloid leukemia. The frequency of leukemic evolution varies according to myeloproliferative neoplasms subtype. It is highest in primary myelofibrosis, where it is estimated to be approximately 10–20% at 10 years, following by polycythemia vera, with a risk of 2.3% at 10 years and 7.9% at 20 years. In essential thrombocythemia, however, transformation to acute myeloid leukemia is considered relatively uncommon. Different factors are associated with leukemic evolution in myeloproliferative neoplasms, but generally include advanced age, leukocytosis, exposure to myelosuppressive therapy, cytogenetic abnormalities, as well as increased number of mutations in genes associated with myeloid neoplasms. The prognosis of these patients is dismal, with a medium overall survival ranging from 2.6–7.0 months. Currently, there is no standard of care for managing the blast phase of these diseases, and no treatment to date has consistently led to prolonged survival and/or hematological remission apart from an allogeneic stem cell transplant. Nevertheless, new targeted agents are currently under development. In this review, we present the current evidence regarding risk factors, molecular characterization, and treatment options for this critical subset of myeloproliferative neoplasms patients.

Myelofibrosis osteoclasts are clonal and functionally impaired

Bone marrow (BM) sclerosis is commonly found in patients with late-stage myelofibrosis (MF). Because osteoclasts (OCs) and osteoblasts play a key role in bone remodeling, and MF monocytes, the OC precursors, are derived from the neoplastic clone, we wondered whether decreased OC numbers or impairment in their osteolytic function affects the development of osteosclerosis. Analysis of BM biopsies from 50 MF patients showed increased numbers of multinucleated tartrate-resistant acid phosphatase (TRAP)/cathepsin K⁺ OCs expressing phosphorylated Janus kinase 2 (JAK2). Randomly microdissected TRAP⁺ OCs from 16 MF patients harbored JAK2 or calreticulin (CALR) mutations, confirming MF OCs are clonal. To study OC function, CD14⁺ monocytes from MF patients and healthy individuals were cultured and differentiated into OCs. Unlike normal OCs, MF OCs appeared small and round, with few protrusions, and carried the mutations and chromosomal abnormalities of neoplastic clones. In addition, MF OCs lacked F-actin-rich ring-like structures and had fewer nuclei and reduced colocalization signals, compatible with decreased fusion events, and their mineral resorption capacity was significantly reduced, indicating impaired osteolytic function. Taken together, our data suggest that, although the numbers of MF OCs are increased, their impaired osteolytic activity distorts bone remodeling and contributes to the induction of osteosclerosis.

Utility of JAK2 V617F allelic burden in distinguishing chronic myelomonocytic Leukemia from Primary myelofibrosis with monocytosis

The concurrent presence of JAK2 V617F, monocytosis, and bone marrow fibrosis can be observed in both chronic myelomonocytic leukemia (CMML) and primary myelofibrosis (PMF). It can be challenging to distinguish CMML with JAK2 mutation and fibrosis from other myeloid neoplasms, particularly PMF. To identify key features that may help distinguish these 2 entities, we retrospectively studied 21 cases diagnosed as "CMML" with JAK2 V617F and bone marrow fibrosis that were identified from a cohort of 610 cases of CMML diagnosed in 2006 to 2016. Upon further review, we confirmed the diagnosis of CMML in 7 cases, 11 cases were reclassified as PMF, and 3 cases had features intermediate between CMML and PMF (gray zone). These 11 cases of PMF with monocytosis featured a higher JAK2 V617F allelic burden (median, 43%; range, 20%-62%) and atypical pleomorphic megakaryocytes with hyperchromatic nuclei. Complete blood count showed more pronounced myeloid left shift. In contrast, 7 CMML cases had significantly lower JAK2 V617F allelic burden (median, 17%; range, 5%-36%; P < .0001) and dysplastic megakaryocytes along with variable degree of dysplasia in other lineages. The median survival of PMF and CMML patients was 32 and 40 months, respectively. We conclude that besides morphology of megakaryocytes and other features, JAK2 V617F allelic burden can help differentiate CMML from PMF with monocytosis. SRSF2 and RAS mutations are observed in both disease categories. Rare gray-zone cases exist with hybrid features.

Expression of CD markers in JAK2V617F positive myeloproliferative neoplasms: Prognostic significance

Myeloproliferative neoplasms (MPNs) are clonal stem cell disorders characterized by the presence of JAK2^V617F mutation. Thrombohemorrhagic as well as autoimmune or inflammatory phenomena are common clinical outcomes of these disorders. Recent studies have shown that abnormality in frequency and function of blood cells manifested by an alteration in CD markers' expression patterns play a key role in these complications. So, there may be a relationship between CD markers' expressions and prognosis of JAK2^V617F positive MPNs. Therefore, in this review, we have focused on these abnormalities from the perspective of changing expressions of CD markers and assessment of the relationship between these changes with prognosis of JAK2^V617F positive MPNs. It can be stated that the abnormal expression of a large number of CD markers can be used as a prognostic biomarker for clinical outcomes including thrombohememorrhagic events, as well as autoimmune and leukemic transformation in JAK2^V617F positive MPNs. Considering the possible role of CD markers' expressions in JAK2^V617F MPNs prognosis, further studies are needed to confirm the relationship between the expression of CD markers with prognosis to be able to find an appropriate therapeutic approach via targeting CD markers.

How I treat myelofibrosis after failure of JAK inhibitors

The introduction of JAK inhibitors, leading to regulatory approval of ruxolitinib, represents a major therapeutic advance in myelofibrosis (MF). Most patients experience reduction in splenomegaly and improved quality of life from symptom improvement. It is a paradox, however, that, despite inhibition of signaling downstream of disease-related driver mutations, JAK inhibitor treatment is not associated with consistent molecular or pathologic responses in MF. Furthermore, there are important limitations to JAK inhibitor therapy including development of dose-limiting cytopenias and/or nonhematological toxicities such as neuropathy or opportunistic infections. Over half of the patients discontinue treatment within 3 years of starting treatment. Although data are sparse, clinical outcome after JAK inhibitor "failure" is likely poor; consequently, it is important to understand patterns of failure to select appropriate salvage treatment(s). An algorithmic approach, particularly one that incorporates cytogenetics/molecular data, is most helpful in selecting stem cell transplant candidates. Treatment of transplant-ineligible patients relies on a problem-based approach that includes use of investigational drugs, or consideration of splenectomy or radiotherapy. Data from early phase ruxolitinib combination studies, despite promising preclinical data, have not shown clear benefit over monotherapy thus far. Development of effective treatment strategies for MF patients failing JAK inhibitors remains a major unmet need.

Myeloid neoplasms with features intermediate between primary myelofibrosis and chronic myelomonocytic leukemia

Monocytosis can develop during disease course in primary myelofibrosis simulating that seen in chronic myelomonocytic leukemia, and should not lead to disease reclassification. In contrast, at presentation, rare cases have clinical, morphologic, and molecular genetic features truly intermediate between primary myelofibrosis and chronic myelomonocytic leukemia. The taxonomy and natural history of these diseases are unclear. We identified cases which either: (1) fulfilled the 2008 World Health Organization criteria for primary myelofibrosis but had absolute monocytosis and, when available, chronic myelomonocytic leukemia-related mutations (ASXL1, SRSF2, TET2) or (2) fulfilled criteria of chronic myelomonocytic leukemia but had megakaryocytic proliferation and atypia, marrow fibrosis, and myeloproliferative-type driver mutations (JAK2, MPL, CALR). Patients with established primary myelofibrosis who developed monocytosis and those with chronic myelomonocytic leukemia with marrow fibrosis were excluded. By combining the pathology databases of two large institutions, six eligible cases were identified. Patients were predominantly male and elderly with monocytosis at diagnosis (average 17.5%/2.3 × 10³/μl), organomegaly, primary myelofibrosis-like atypical megakaryocytes admixed with a variable number of chronic myelomonocytic leukemia-like hypolobated forms, variable myelodysplasia, marrow fibrosis and osteosclerosis. All had a normal karyotype and no myelodysplasia-associated cytogenetic abnormalities. Five of the patients in whom a more extensive molecular characterization was performed showed co-mutations involving JAK2 or MPL and ASXL1, SRSF2, TET2, NRAS, and/or KRAS. Disease progression has occurred in all and two have died. Rare patients present with features that overlap between primary myelofibrosis and chronic myelomonocytic leukemia and are thus difficult to classify based on current World Health Organization criteria. Biologically, these cases likely represent primary myelofibrosis with monocytosis, dysplasia, and secondary (non-driver) mutations at presentation. Alternatively, they may represent a true gray zone of neoplasms. Their clinical behavior appears aggressive and innovative therapeutic approaches may be beneficial in this particular subset.

How I investigate monocytosis

Monocytosis is a common finding that is caused by a wide variety of neoplastic and non-neoplastic conditions. The adequate evaluation of monocytosis involves the integration of laboratory data, morphology, clinical findings, and the judicious use of ancillary studies. We review the literature on monocytosis, including the 2017 revised 4th edition of the World Health Organization classification of hematopoietic neoplasms. We present a review of monocytosis with practical guidelines on how to approach both routine and challenging cases.

Bone marrow fibrosis in chronic myelomonocytic leukemia is associated with increased megakaryopoiesis, splenomegaly and with a shorter median time to disease progression

Bone marrow (BM) fibrosis is an adverse prognostic marker in several myeloid neoplasms, particularly in myelodysplastic syndrome (MDS) with fibrosis; however, its significance in chronic myelomonoctyic leukemia (CMML) has not been evaluated. We performed a retrospective analysis to investigate the prognostic and clinicopathological features of CMML with and without BM fibrosis. The study included specimens from a total of 83 untreated CMML patients from 2 large institutions. Patients with any amount of BM fibrosis (MF-1 or higher; MF1+) had significantly shorter progression-free survival (MF1+, 28.3 months vs MF0, not reached; p = 0.001, log rank test), splenomegaly (p = 0.016), and increased BM megakaryocytes (p = 0.04) compared to patients without BM fibrosis (MF-0). No association was observed between fibrosis and peripheral blood parameters, presence of JAK2 V617F mutation, BM blasts, or overall survival. Our study demonstrates the importance of assessing BM fibrosis in CMML. Similar to MDS, the presence of BM fibrosis may identify a distinct subgroup of CMML patients (CMML-F) with a more aggressive clinical course.

The 2016 revision to the World Health Organization classification of myeloid neoplasms and acute leukemia

The World Health Organization (WHO) classification of tumors of the hematopoietic and lymphoid tissues was last updated in 2008. Since then, there have been numerous advances in the identification of unique biomarkers associated with some myeloid neoplasms and acute leukemias, largely derived from gene expression analysis and next-generation sequencing that can significantly improve the diagnostic criteria as well as the prognostic relevance of entities currently included in the WHO classification and that also suggest new entities that should be added. Therefore, there is a clear need for a revision to the current classification. The revisions to the categories of myeloid neoplasms and acute leukemia will be published in a monograph in 2016 and reflect a consensus of opinion of hematopathologists, hematologists, oncologists, and geneticists. The 2016 edition represents a revision of the prior classification rather than an entirely new classification and attempts to incorporate new clinical, prognostic, morphologic, immunophenotypic, and genetic data that have emerged since the last edition. The major changes in the classification and their rationale are presented here.