The mutational landscape of 18 investigated genes clearly separates four subtypes of myelodysplastic/myeloproliferative neoplasms

Analytical Validation of a 37-Gene Next-Generation Sequencing Panel for Myeloid Malignancies and Review of Initial Findings Incorporating Updated 2022 Diagnostic and Prognostic Guidelines

Myeloid neoplasms are clonal disorders that arise via acquisition of genetic mutations leading to excessive proliferation and defective differentiation. Mutational profiling is vital as it has implications for diagnosis, prognosis, and therapeutic decision-making. Next-generation sequencing (NGS) has become a mainstay in the evaluation of myeloid malignancies, as it enables efficient characterization of multiple genetic changes. Herein, the analytical validation of the 37-gene Archer VariantPlex Core Myeloid panel is reported, using 58 DNA specimens with 87 single-nucleotide variants and 23 insertions/deletions. The panel achieved good depth of coverage, 100% analytical sensitivity and specificity for single-nucleotide variants and insertions/deletions ≤21 bp, and 100% reproducibility, with a reportable limit of detection determined as 5%. The Archer NGS panel can accurately and reproducibly detect variants of clinical significance in myeloid neoplasms. A retrospective analysis of 535 clinical specimens tested with the Archer NGS panel showed a frequency and pattern of mutations across myeloid malignancies that were similar to other published studies. A review of the diagnostic classification of patients with acute myeloid leukemia and myelodysplastic syndrome using the World Health Organization 2017/2022 and International Consensus Classification 2022 guidelines, in addition to European LeukemiaNet 2017/2022 risk stratification of patients with acute myeloid leukemia, was also performed to assess the utility of the molecular information provided by the Archer NGS panel.

Chronic neutrophilic leukemia and atypical chronic myeloid leukemia: 2024 update on diagnosis, genetics, risk stratification, and management

Chronic neutrophilic leukemia (CNL) is a rare BCR::ABL1-negative myeloproliferative neoplasm (MPN) defined by persistent mature neutrophilic leukocytosis and bone marrow granulocyte hyperplasia. Atypical chronic myeloid leukemia (aCML) (myelodysplastic "[MDS]/MPN with neutrophilia" per World Health Organization [WHO]) is a MDS/MPN overlap disorder featuring dysplastic neutrophilia and circulating myeloid precursors. Both manifest with frequent hepatosplenomegaly and less commonly, bleeding, with high rates of leukemic transformation and death. The 2022 revised WHO classification conserved CNL diagnostic criteria of leukocytosis ≥25 × 109/L, neutrophils ≥80% with <10% circulating precursors, absence of dysplasia, and presence of an activating CSF3R mutation. ICC criteria are harmonized with those of other myeloid entities, with a key distinction being lower leukocytosis threshold (≥13 × 109/L) for cases CSF3R-mutated. Criteria for aCML include leukocytosis ≥13 × 109/L, dysgranulopoiesis, circulating myeloid precursors ≥10%, and at least one cytopenia for MDS-thresholds (ICC). In both classifications ASXL1 and SETBP1 (ICC), or SETBP1 ± ETNK1 (WHO) mutations can be used to support the diagnosis. Both diseases show hypercellular bone marrow due to a granulocytic proliferation, aCML distinguished by dysplasia in granulocytes ± other lineages. Absence of monocytosis, rare/no basophilia, or eosinophilia, <20% blasts, and exclusion of other MPN, MDS/MPN, and tyrosine kinase fusions, are mandated. Cytogenetic abnormalities are identified in ~1/3 of CNL and ~15-40% of aCML patients. The molecular signature of CNL is a driver mutation in colony-stimulating factor 3 receptor-classically T618I, documented in >80% of cases. Atypical CML harbors a complex genomic backdrop with high rates of recurrent somatic mutations in ASXL1, SETBP1, TET2, SRSF2, EZH2, and less frequently in ETNK1. Leukemic transformation rates are ~10-25% and 30-40% for CNL and aCML, respectively. Overall survival is poor: 15-31 months in CNL and 12-20 months in aCML. The Mayo Clinic CNL risk model for survival stratifies patients according to platelets <160 × 109/L (2 points), leukocytes >60 × 109/L (1 point), and ASXL1 mutation (1 point); distinguishing low- (0-1 points) versus high-risk (2-4 points) categories. The Mayo Clinic aCML risk model attributes 1 point each for: age >67 years, hemoglobin <10 g/dL, and TET2 mutation, delineating low- (0-1 risk factor) and high-risk (≥2 risk factors) subgroups. Management is risk-driven and symptom-directed, with no current standard of care. Most commonly used agents include hydroxyurea, interferon, Janus kinase inhibitors, and hypomethylating agents, though none are disease-modifying. Hematopoietic stem cell transplant is the only potentially curative modality and should be considered in eligible patients. Recent genetic profiling has disclosed CBL, CEBPA, EZH2, NRAS, TET2, and U2AF1 to represent high-risk mutations in both entities. Actionable mutations (NRAS/KRAS, ETNK1) have also been identified, supporting novel agents targeting involved pathways. Preclinical and clinical studies evaluating new drugs (e.g., fedratinib, phase 2) and combinations are detailed.

Myeloproliferative Neoplasms: Contemporary Review and Molecular Landscape

Myelofibrosis (MF), Myeloproliferative neoplasms (MPNs), and MDS/MPN overlap syndromes have a broad range of clinical presentations and molecular abnormalities, making their diagnosis and classification complex. This paper reviews molecular aberration, epigenetic modifications, chromosomal anomalies, and their interactions with cellular and other immune mechanisms in the manifestations of these disease spectra, clinical features, classification, and treatment modalities. The advent of new-generation sequencing has broadened the understanding of the genetic factors involved. However, while great strides have been made in the pharmacological treatment of these diseases, treatment of advanced disease remains hematopoietic stem cell transplant.

Research progress of additional pathogenic mutations in chronic neutrophilic leukemia

Chronic neutrophilic leukemia (CNL) is a rare type of myeloproliferative neoplasm (MPN). Due to its nonspecific clinical symptoms and lack of specific molecular markers, it was previously difficult to distinguish it from other diseases with increased neutrophils. However, the discovery of the CSF3R mutation in CNL 10 years ago and the update of the diagnostic criteria by the World Health Organization (WHO) in 2016 brought CNL into a new era of molecular diagnosis. Next-generation sequencing (NGS) technology has led to the identification of numerous mutant genes in CNL. While CSF3R is commonly recognized as the driver mutation of CNL, other mutations have also been detected in CNL using NGS, including mutations in other signaling pathway genes (CBL, JAK2, NARS, PTPN11) and chromatin modification genes (ASXL1, SETBP1, EZH2), DNA methylation genes (DNMT3A, TET2), myeloid-related transcription factor genes (RUNX1, GATA2), and splicing and RNA metabolism genes (SRSF2, U2AF1). The coexistence of these mutated genes and CSF3R mutations, as well as the different evolutionary sequences of clones, deepens the complexity of CNL molecular biology. The purpose of this review is to summarize the genetic research findings of CNL in the last decade, focusing on the common mutated genes in CNL and their clinical significance, as well as the clonal evolution pattern and sequence of mutation acquisition in CNL, to provide a basis for the appropriate management of CNL patients.

Myelodysplastic Syndromes/Myeloproliferative Overlap Neoplasms and Differential Diagnosis in the WHO and ICC 2022 Era: A Focused Review

The myelodysplastic syndromes/myeloproliferative neoplasms (MDS/MPN) category comprises a varied group of myeloid neoplastic diseases characterized by clinical and pathologic overlapping features of both myelodysplastic and myeloproliferative neoplasms. For these reasons, these tumors are challenging in terms of diagnosis. The recent World Health Organization (WHO) 2022 classification and the International Consensus Classification (ICC) made changes in the classification of MDS/MPN compared to the previous 2016 WHO classification and improved the diagnostic criteria of these entities. The aim of this review is to describe the main entities reported in the more recent classifications, focusing on chronic myelomonocytic leukemia (CMML), MDS/MPN with neutrophilia (or atypical CML [aCML]), and MDS/MPN with SF3B1 mutation and thrombocytosis/MDS/MPN with ring sideroblasts and thrombocytosis. A particular emphasis is given to the differential diagnosis and analysis of subtle divergences and semantic differences between the WHO classification and the ICC for these entities.

Genomics of myelodysplastic/myeloproliferative neoplasm

Myelodysplastic/ Myeloproliferative neoplasms (MDS/MPN) demonstrate overlapping pathologic and molecular features of myelodysplastic (MDS) and myeloproliferative (MPN) neoplasms. Diagnosis is difficult based on morphology alone, requiring exclusion of various non-neoplastic causes for CBC abnormalities and morphologic findings and other myeloid neoplasms. Identifying a clonal abnormality by cytogenetics or molecular studies has vastly improved our ability to diagnose MDS/MPN and has been incorporated in the different classification schemas. Currently two separate classification systems are in use- The 5^th edition WHO and international consensus classification. The two competing classifications emphasize genetic work-up and are similar on many levels; however, they do introduce diagnostic dilemma when diagnosing certain entities such as chronic myelomonocytic leukemia in the presence of NPM1 mutations. The genetic profile overlaps among different subentities; however, the combination and the incidence of mutations; together with the clinical features and morphology helps in further subclassification. In this review, we discuss the advances in molecular characterization of MDS/MPN. We attempt to summarize the differences between the various classification schemes, and highlight the changes made in the diagnostic criteria.

Atypical chronic myeloid leukemia and myelodysplastic/myeloproliferative neoplasm, not otherwise specified: 2023 update on diagnosis, risk stratification, and management

DISEASE OVERVIEW

Atypical chronic myeloid leukemia (aCML) and myelodysplastic/myeloproliferative (MDS/MPN) neoplasms, not otherwise specified (NOS), are MDS/MPN overlap neoplasms characterized by leukocytosis, in the absence of monocytosis and eosinophilia, with <20% blasts in the blood and bone marrow.

DIAGNOSIS

aCML, previously known as aCML, BCR::ABL1 negative, was renamed as aCML by the ICC classification, and as MDS/MPN with neutrophilia by the 5th edition of the WHO classification. This entity is characterized by dysplastic neutrophilia with immature myeloid cells comprising ≥10% of the white blood cell count, with prominent dysgranulopoiesis. MDS/MPN-NOS consists of MDS/MPN overlap neoplasms not meeting criteria for defined categories such as chronic myelomonocytic leukemia (CMML), MDS/MPN-ring sideroblasts-thrombocytosis (MDS/MPN-RS-T), and aCML.

MUTATIONS AND KARYOTYPE

Cytogenetic abnormalities are seen in 40-50% of patients in both categories. In aCML, somatic mutations commonly encountered include ASXL1, SETBP1, ETNK1, and EZH2 whereas MDS/MPN-NOS can be further stratified by mutational profiles into CMML-like, MDS/MPN-RS-T-like, aCML-like, TP35-mutated, and "others", respectively.

RISK STRATIFICATION

The Mayo Clinic aCML model stratifies patients based on age >67 years, hemoglobin <10 g/dl, and the presence of TET2 mutations into low-risk (0-1 points) and high-risk (>2 points) groups, with median survivals of 18 and 7 months, respectively. MDS/MPN-NOS patients have traditionally been risk stratified using MDS risk models such as IPSS and IPSS-R.

TREATMENT

Leukocytosis and anemia are managed like lower risk MPN and MDS. DNMT inhibitors have been used in both entities with suboptimal response rates. Allogeneic stem cell transplant remains the only curative strategy but is associated with high morbidity and mortality.

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).

Disease and Clinical Characteristics of Patients With a Clinical Diagnosis of Myelofibrosis Enrolled in the MOST Study

BACKGROUND

Clinical characteristics and treatment patterns of patients with lower-risk myelofibrosis (MF) are not well described. This analysis from the MOST (NCT02953704) assessed the demographic and clinical characteristics and treatment patterns of patients with the clinical diagnosis of lower-risk MF at enrollment.

PATIENTS AND METHODS

MOST is an ongoing, prospective, observational study in patients with clinical diagnoses of MF or essential thrombocythemia enrolled at clinical practices throughout the United States. Patients included in the MF cohort (≥18 years of age) had low-risk MF by the Dynamic International Prognostic Scoring System or intermediate-1 (INT-1) risk MF (by age >65 years only) at enrollment. Patient data were entered into an electronic case report form during usual-care visits over a planned 36 month observation period.

RESULTS

Two hundred five patients were eligible for this analysis (low risk, n = 85; INT-1 risk, n = 120; median age, 68 years [range, 35-88]); 166 patients (81.0%) had mutation testing results available. The median time from MF diagnosis to enrollment was 1.8 years. Hemoglobin and hematocrit levels were below the normal range in 50.5% and 48.7% of patients, respectively. Nearly all (98.0%) patients had comorbid conditions, most commonly hypertension (49.8%). Fatigue was the most common physician-reported MF symptom (30.7%). At enrollment, 55.6% of patients were receiving MF-directed monotherapy, most frequently hydroxyurea (46.5%) or ruxolitinib (40.4%).

CONCLUSION

Future longitudinal analyses of data from MOST will help identify unmet needs and characterize how patients with lower-risk MF are managed throughout the disease course.

Myelodysplastic/myeloproliferative neoplasms-unclassifiable with isolated isochromosome 17q represents a distinct clinico-biologic subset: a multi-institutional collaborative study from the Bone Marrow Pathology Group

Classification of myeloid neoplasms with isolated isochromosome i(17q) [17p deletion with inherent monoallelic TP53 loss plus 17q duplication] is controversial. Most cases fall within the WHO unclassifiable myelodysplastic/myeloproliferative neoplasms (MDS/MPN-U) category. The uniformly dismal outcomes warrant better understanding of this entity. We undertook a multi-institutional retrospective study of 92 adult MDS/MPN-U cases from eight institutions. Twenty-nine (32%) patients had isolated i(17q) [MDS/MPN-i(17q)]. Compared to MDS/MPN without i(17q), MDS/MPN-i(17q) patients were significantly younger, had lower platelet and absolute neutrophil counts, and higher frequency of splenomegaly and circulating blasts. MDS/MPN-i(17q) cases showed frequent bilobed neutrophils (75% vs. 23%; P = 0.03), hypolobated megakaryocytes (62% vs. 20%; P = 0.06), and a higher frequency of SETBP1 (69% vs. 5%; P = 0.002) and SRSF2 (63% vs. 5%; P = 0.006) mutations that were frequently co-existent (44% vs. 0%; P = 0.01). TP53 mutations were rare. The mutation profile of MDS/MPN-U-i(17q) was similar to other myeloid neoplasms with i(17q) including atypical chronic myeloid leukemia, chronic myelomonocytic leukemia, myelodysplastic/myeloproliferative neoplasm with ring sideroblasts and thrombocytosis, myelodysplastic syndrome and acute myeloid leukemia, with frequent concomitant SETBP1/SRSF2 mutations observed across all the diagnostic entities. Over a median follow-up of 52 months, patients with MDS/MPN-i(17q) showed a shorter median overall survival (11 vs. 28 months; P < 0.001). The presence of i(17q) retained independent poor prognostic value in multivariable Cox-regression analysis [HR 3.686 (1.17-11.6); P = 0.026] along with splenomegaly. We suggest that MDS/MPN-i(17q) warrants recognition as a distinct subtype within the MDS/MPN-U category based on its unique clinico-biologic features and uniformly poor prognosis.

Molecular Pathogenesis of BCR-ABL-Negative Atypical Chronic Myeloid Leukemia

Atypical chronic myeloid leukemia is a rare disease whose pathogenesis has long been debated. It currently belongs to the group of myelodysplastic/myeloproliferative disorders. In this review, an overview on the current knowledge about diagnosis, prognosis, and genetics is presented, with a major focus on the recent molecular findings. We describe here the molecular pathogenesis of the disease, focusing on the mechanisms of action of the main mutations as well as on gene expression profiling. We also present the treatment options focusing on emerging targeted therapies.

A Phase I trial of talazoparib in patients with advanced hematologic malignancies

Aim:

The objective of this study was to establish the maximum tolerated dose (MTD), safety, pharmacokinetics, and anti-leukemic activity of talazoparib.

Patients & methods:

This Phase I, two-cohort, dose-escalation trial evaluated talazoparib monotherapy in advanced hematologic malignancies (cohort 1: acute myeloid leukemia/myelodysplastic syndrome; cohort 2: chronic lymphocytic leukemia/mantle cell lymphoma).

Results:

Thirty-three (cohort 1: n = 25; cohort 2: n = 8) patients received talazoparib (0.1–2.0 mg once daily). The MTD was exceeded at 2.0 mg/day in cohort 1 and at 0.9 mg/day in cohort 2. Grade ≥3 adverse events were primarily hematologic. Eighteen (54.5%) patients reported stable disease.

Conclusion:

Talazoparib is relatively well tolerated in hematologic malignancies, with a similar MTD as in solid tumors, and shows preliminary anti leukemic activity.

Clinical trial registration: NCT01399840 (ClinicalTrials.gov)

The objective of this study was to define the highest dose of talazoparib that people with various types of leukemia (mainly various blood cancers) could tolerate. People were assigned into two cohorts based on their type of leukemia: cohort 1 included 25 people with acute myeloid leukemia or myelodysplastic syndrome; cohort 2 included 8 people with chronic lymphocytic leukemia or mantle cell lymphoma. Similar to what researchers observed for people with solid tumors, the highest tolerated dose was 1.35 mg per day in cohort 1, and it was estimated to be ∼0.9 mg per day in cohort 2. Side effects that occurred during the study were expected, given the types of leukemia being treated. Talazoparib also showed promising anti leukemic effects in some patients.

In this Phase I talazoparib trial in hematologic malignancies (cohort 1: AML/MDS, n = 25; cohort 2: CLL/MCL, n = 8), the maximum tolerated dose was exceeded at 2.0 and 0.9 mg/day in cohorts 1 and 2, respectively. Stable disease and transfusion independence were also observed.

Pathogenic Mutations and Atypical Flow Cytometric Findings Characterize the Majority of Unclassifiable Myelodysplastic/Myeloproliferative Neoplasms

OBJECTIVES

Myelodysplastic/myeloproliferative neoplasms (MDS/MPN) are a group of rare and heterogeneous hematopoietic disorders that frequently present a diagnostic challenge. Here we present our institutional experience with next-generation sequencing (NGS), together with morphologic, flow cytometric, and cytogenetic evaluation, in the diagnosis of MDS/MPN, with particular emphasis on MDS/MPN unclassifiable (MPN-U).

METHODS

We evaluated the morphologic, flow cytometric, cytogenetic, and molecular characteristics of all MDS/MPN cases that underwent NGS at our institution between April 2016 and February 2019.

RESULTS

Thirty-seven cases of MDS/MPN were identified, including 14 cases of MDS/MPN-U. Ninety-seven percent harbored mutations and immunophenotypic aberrancies (36/37), while only 38% had cytogenetic abnormalities (12/32). The MDS/MPN-U group had the highest rate of myeloblast phenotypic abnormalities and had a high mutation rate of approximately 2.7 mutated genes per case, most commonly in JAK2, SRSF2, and ASXL1.

CONCLUSIONS

No single ancillary study was abnormal in every case, but all cases had at least one abnormal finding, demonstrating the usefulness of a multiparameter approach to the diagnosis of MDS/MPN. Although a few specific mutations were found exclusively in MDS/MPN-U and JAK2 mutations were most prevalent, larger studies are needed to determine whether MDS/MPN-U has a mutational "fingerprint," which may aid in diagnosis and targeted therapy.

Examining disease boundaries: Genetics of myelodysplastic/myeloproliferative neoplasms

Myelodysplastic/myeloproliferative neoplasms (MDS/MPN) are clonal myeloid malignancies that are characterized by dysplasia resulting in cytopenias as well as proliferative features such as thrombocytosis or splenomegaly. Recent studies have better defined the genetics underlying this diverse group of disorders. Trisomy 8, monosomy 7, and loss of Y chromosome are the most common cytogenetic abnormalities seen. Chronic myelomonocytic leukemia (CMML) likely develops from early clones with TET2 mutations that drive granulomonocytic differentiation. Mutations in SRSF2 are common and those in the RAS-MAPK pathway are typically implicated in disease with a proliferative phenotype. Several prognostic systems have incorporated genetic features, with ASXL1 most consistently demonstrating worse prognosis. Atypical chronic myeloid leukemia (aCML) is most known for granulocytosis with marked dysplasia and often harbors ASXL1 mutations, but SETBP1 and ETNK1 are more specific to this disease. MDS/MPN with ring sideroblasts and thrombocytosis (MDS/MPN-RS-T) most commonly involves spliceosome mutations (namely SF3B1) and mutations in the JAK-STAT pathway. Finally, MDS/MPN-unclassifiable (MDS/MPN-U) is least characterized but a significant fraction carries mutations in TP53. The remaining patients have clinical and/or genetic features similar to the other MDS/MPNs, suggesting there is room to better characterize this entity. Evolution from age-related clonal hematopoiesis to MDS/MPN likely depends on the order of mutation acquisition and interactions between various biologic factors. Genetics will continue to play a critical role in our understanding of these illnesses and advancing patient care.

Gender-related differences in the outcomes and genomic landscape of patients with myelodysplastic syndrome/myeloproliferative neoplasm overlap syndromes

Myelodysplastic syndrome/myeloproliferative neoplasm (MDS/MPN) overlap syndromes show a male predominance and men with MDS/MPN have worse outcomes, but it is unknown if the mutational burden differs between genders. We reviewed 167 patients with MDS/MPN and found that men had worse overall survival [hazard ratio (HR) 2·09, 95% confidence interval (CI) 1·16-3·75; P = 0·013] independent of subtype, Revised International Prognostic Scoring System score and age at diagnosis. We analysed the genomic data of a subset of 100 patients. Men had 0·88 more somatic mutations on average (95% CI 0·20-1·56, P = 0·011) independent of subtype, sample source and blast percentage. More somatic mutations was associated with a higher incidence of transformation to acute myeloid leukaemia (subdistribution HR 1·30, 95% CI 1·01-1·70; P = 0·046). Men had 0·70 more mutations in high-risk genes [additional sex combs like-1 (ASXL1), enhancer of zeste homolog 2 (EZH2), Runt-related transcription factor 1 (RUNX1), SET binding protein 1 (SETBP1), NRAS proto-oncogene, GTPase (NRAS), stromal antigen 2 (STAG2)] on average (95% CI 0·11-1·29, P = 0·021), and 13-times higher odds of harbouring an EZH2 mutation (95% CI 1·64-102·94, P = 0·015). The presence of an EZH2 mutation was associated with worse survival among men (HR 2·98, 95% CI 1·1-8·0; P = 0·031). Our present findings suggest that the worse outcomes in men with MDS/MPN are associated with a higher number of somatic mutations, especially in high-risk genes. These results warrant validation in larger cohorts and investigation of the underlying mechanisms.

Myelodysplastic syndromes and overlap syndromes

Myelodysplastic syndromes (MDS) are a heterogeneous group of clonal hematological neoplasms characterized by ineffective hematopoiesis, morphologic dysplasia, and cytopenia. MDS overlap syndromes include various disorders, such as myelodysplastic/myeloproliferative neoplasms and hypoplastic MDS with aplastic anemia characteristics. MDS overlap syndromes share the characteristics of other diseases, which make differential diagnoses challenging. Advances in genomic studies have led to the discovery of frequent mutations in MDS and overlap syndromes; however, most of the mutations are not specific for the diagnosis of these diseases. The molecular characteristics of the overlap syndromes usually do not show a just “in-between” form but rather heterogeneous features. Established diagnostic criteria for these diseases based on clinical, morphologic, and laboratory features are still useful when combined with genomic data. It is expected that further studies for MDS and overlap syndromes will place emphasis on the roles of mutations as therapeutic targets and prognostic indicators.

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.

Traipsing Through Muddy Waters: A Critical Review of the Myelodysplastic Syndrome/Myeloproliferative Neoplasm (MDS/MPN) Overlap Syndromes

Myelodysplastic syndrome/Myeloproliferative neoplasms (MDS/MPNs) are molecularly complex, clinically heterogeneous diseases that exhibit proliferative and dysplastic features. Diagnostic criteria use clinical, pathologic, and genomic features to distinguish between disease entities, though considerable clinical and genetic overlap persists. MDS/MPNs are associated with a poor prognosis, save for MDS/MPN with ring sideroblasts and thrombocytosis, which can behave more indolently. The current treatment approach is risk-adapted and symptom-directed and largely extrapolated from experience in MDS or MPN. Gene sequencing has demonstrated frequent mutations involving signaling, epigenetic, and splicing pathways, which present numerous therapeutic opportunities for clinical investigation.

Chronic myeloid neoplasms harboring concomitant mutations in myeloproliferative neoplasm driver genes (JAK2/MPL/CALR) and SF3B1

JAK2, CALR, and MPL are myeloproliferative neoplasm (MPN)-driver mutations, whereas SF3B1 is strongly associated with ring sideroblasts (RS) in myelodysplastic syndrome (MDS). Concomitant mutations of SF3B1 and MPN-driver mutations out of the context of MDS/MPN with RS and thrombocytosis (MDS/MPN-RS-T) are not well-studied. From the cases (<5% blasts) tested by NGS panels interrogating at least 42 myeloid neoplasm-related genes, we identified 18 MDS/MPN-RS-T, 42 MPN, 10 MDS, and 6 MDS/MPN-U cases with an SF3B1 and an MPN-driver mutation. Using a 10% VAF difference to define "SF3B1-dominant," "MPN-mutation dominant," and "no dominance," the majority of MDS/MPN-RS-T clustered in "SF3B1-dominant" and "no dominance" regions. Aside from parameters as thrombocytosis and ≥15% RS required for RS-T, MDS also differed in frequent neutropenia, multilineage dysplasia, and notably more cases with <10% VAF of MPN-driver mutations (60%, p = 0.0346); MPN differed in more frequent splenomegaly, myelofibrosis, and higher VAF of "MPN-driver mutations." "Gray zone" cases with features overlapping MDS/MPN-RS-T were observed in over one-thirds of non-RS-T cases. This study shows that concomitant SF3B1 and MPN-driver mutations can be observed in MDS, MPN, and MDS/MPN-U, each showing overlapping but also distinctively different clinicopathological features. Clonal hierarchy, cytogenetic abnormalities, and additional somatic mutations may in part contribute to different disease phenotypes, which may help in the classification of "gray zone" cases.

Genetic complexity of chronic myelomonocytic leukemia

In recent years CMML has received increased attention as the most commonly observed MDS/MPN overlap syndrome. Renewed interest has occurred in part due to widespread adoption of next-generation sequencing panels that help render the diagnosis in the absence of morphologic dysplasia. Although most CMML patients exhibit somatic mutations in epigenetic modifiers, spliceosome components, transcription factors and signal transduction genes, it is increasingly clear that a small subset harbors an inherited predisposition to CMML and other myeloid neoplasms. More intriguing is the fact that the mutational spectrum observed in CMML is found in other types of myeloid leukemias, begging the question of how similar genetic backgrounds can lead to such divergent clinical phenotypes. In this review we present a contemporary snapshot of the genetic complexity inherent to CMML, explore the relationship between genotype-phenotype and present a stepwise model of CMML pathogenesis and progression.

Genomics of myelodysplastic syndrome/myeloproliferative neoplasm overlap syndromes

Myelodysplastic syndrome (MDS)/myeloproliferative neoplasm (MPN) overlap syndromes are uniquely classified neoplasms occurring in both children and adults. This category consists of 5 neoplastic subtypes: chronic myelomonocytic leukemia (CMML), juvenile myelomonocytic leukemia (JMML), BCR-ABL1-negative atypical chronic myeloid leukemia (aCML), MDS/MPN-ring sideroblasts and thrombocytosis (MDS/MPN-RS-T), and MDS/MPN-unclassifiable (U). Cytogenetic abnormalities and somatic copy number variations are uncommon; however, >90% patients harbor gene mutations. Although no single gene mutation is specific to a disease subtype, certain mutational signatures in the context of appropriate clinical and morphological features can be used to establish a diagnosis. In CMML, mutated coexpression of TET2 and SRSF2 results in clonal hematopoiesis skewed toward monocytosis, and the ensuing acquisition of driver mutations including ASXL1, NRAS, and CBL results in overt disease. MDS/MPN-RS-T demonstrates features of SF3B1-mutant MDS with ring sideroblasts (MDS-RS), with the development of thrombocytosis secondary to the acquisition of signaling mutations, most commonly JAK2V617F. JMML, the only pediatric entity, is a bona fide RASopathy, with germline and somatic mutations occurring in the oncogenic RAS pathway giving rise to disease. BCR-ABL1-negative aCML is characterized by dysplastic neutrophilia and is enriched in SETBP1 and ETNK1 mutations, whereas MDS/MPN-U is the least defined and lacks a characteristic mutational signature. Molecular profiling also provides prognostic information, with truncating ASXL1 mutations being universally detrimental and germline CBL mutations in JMML showing spontaneous regression. Sequencing information in certain cases can help identify potential targeted therapies (IDH1, IDH2, and splicing mutations) and should be a mainstay in the diagnosis and management of these neoplasms.

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.

Ruxolitinib Plus Decitabine Effectively Treats Myelodysplastic Syndrome/Myeloproliferative Neoplasm, Unclassifiable, by Decreasing the Variant Allele Frequency of KRAS

Myelodysplastic syndrome/myeloproliferative neoplasm, unclassifiable (MDS/MPN-U) is a subtype of MDS/MPN that exhibits a combination of the features of both MDS and MPN. To date, no curative treatment is available for MDS/MPN-U; however, previous studies have suggested a potential survival advantage for ruxolitinib and hypomethylating agents. We reported a case of a JAK2-negative but KRAS-positive MDS/MPN-U patient treated with ruxolitinib plus decitabine. After treatment, the patient’s clinical symptoms were moderated, and the size of the spleen and the peripheral blood cell counts were reduced. These effects might be due to the regimen’s ability to reduce STAT5 activation and upregulate microRNA-181c to downregulate the variant allele frequency (VAF) of KRAS.

Myelodysplastic/myeloproliferative neoplasm, unclassifiable (MDS/MPN-U): More than just a "catch-all" term?

The clinicopathology of MDS and MPN are not mutually exclusive and for this reason the category of myelodysplastic syndrome/myeloproliferative neoplasm (MDS/MPN) exists. Several sub-entities have been included under the MDS/MPN umbrella, including MDS/MPN-unclassifiable (MDS/MPN-U) for those cases whose morphologic and clinical phenotype do not meet criteria to be classified as any other MDS/MPN sub-entity. Though potentially regarded as a wastebasket diagnosis, since its integration into myeloid disease classification, MDS/MPN-U has been refined with increasing understanding of the mutational and genomic events that drive particular clinicopathologic phenotypes, even within MDS/MPN-U. The prototypical example is the identification of SF3B1 mutations and its durable association with MDS/MPN with ring sideroblasts and thrombocytosis (MDS/MPN-RS-T), an entity previously buried within, but now a separate category outside of MDS/MPN-U. Continued and enhanced study of those entities under MDS/MPN-U, a perhaps provisional category itself, is likely to progressively identify commonality between many "unclassifiables" to establish a new classifiable diagnosis.

Defining the Boundary Between Myelodysplastic Syndromes and Myeloproliferative Neoplasms

In this article we provide a practical and comprehensive review of myeloid neoplasms with overlapping myelodysplastic (MDS) and myeloproliferative (MPN) features, with emphasis on recent updates in classification, particularly the utility of morphologic, cytogenetic, and molecular findings in better defining and classifying these disease entities. We provide the reader with a summary of the most recent developments and updates that have helped further our understanding of the genomic landscape, clinicopathologic features, and prognostic elements of myeloid neoplasms with MDS/MPN features.

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.

MDS overlap disorders and diagnostic boundaries

Myelodysplastic syndromes (MDS) are clonal diseases defined by clinical, morphologic, and genetic features often shared by related myeloid disorders. The diagnostic boundaries between these diseases can be arbitrary and not necessarily reflective of underlying disease biology or outcomes. In practice, measures that distinguish MDS from related disorders may be difficult to quantify and can vary as disease progression occurs. Patients may harbor findings that are not consistent with a single diagnostic category. Several overlap disorders have been formally described, such as the myelodysplastic/myeloproliferative neoplasms (MDS/MPNs). These disorders are characterized by hematopoietic dysplasia with increased proliferation of monocytes, neutrophils, or platelets. They may have mutational profiles that distinguish them from the disorders they resemble and reflect important differences in pathophysiology. MDS also shares diagnostic borders with other diseases. For example, aplastic anemia and hypoplastic MDS can be difficult to distinguish in patients with pancytopenia and bone marrow hypocellularity. Genetic features may help in this regard, because they can identify differences in prognosis and risk of progression. The boundary between MDS and secondary acute myeloid leukemia (sAML) is arbitrarily defined and has been redefined over the years. Genetic studies have demonstrated that sAML clones can precede clinical progression from MDS by many months, suggesting that MDS with excess blasts could be viewed as an overlap between a dysplastic bone marrow failure syndrome and an oligoblastic leukemia. This review will describe the diagnostic boundaries between MDS, MDS/MPNs, sAML, clonal hematopoiesis of indeterminate potential, clonal cytopenia of undetermined significance, and aplastic anemia and how genetic approaches may help to better define them.

Diagnosis and Treatment of Chronic Myelomonocytic Leukemias in Adults: Recommendations From the European Hematology Association and the European LeukemiaNet

Chronic myelomonocytic leukemia (CMML) is a disease of the elderly, and by far the most frequent overlap myelodysplastic/myeloproliferative neoplasm in adults. Aside from the chronic monocytosis that remains the cornerstone of its diagnosis, the clinical presentation of CMML includes dysplastic features, cytopenias, excess of blasts, or myeloproliferative features including high white blood cell count or splenomegaly. Prognosis is variable, with several prognostic scoring systems reported in recent years, and treatment is poorly defined, with options ranging from watchful waiting to allogeneic stem cell transplantation, which remains the only curative therapy for CMML. Here, we present on behalf of the European Hematology Association and the European LeukemiaNet, evidence- and consensus-based guidelines, established by an international group of experts, from Europe and the United States, for standardized diagnostic and prognostic procedures and for an appropriate choice of therapeutic interventions in adult patients with CMML.

SRSF2 mutations in myelodysplasia/myeloproliferative neoplasms

Recurrent gene mutations have been described with varying frequencies in myelodysplasia (MDS) /myeloproliferative neoplasm (MPN) overlap syndromes (MMOS). Recent work has placed significant focus on understanding the role of gene lesions involving the spliceosomal machinery in leukemogeneis. SRSF2 is a gene encoding critical spliceosomal proteins. SRSF2 mutations appear to play an important role in pathogenesis of MMOS, particularly in chronic myelomonocytic leukemia. Inhibition of splicing may be a new therapeutic approach. E7107, a spliceosome inhibitor, has been shown to differentially inhibit splicing more in SRSF2-mutant cells leading to decreased leukemia burden in mice. H3B-8800 is a small molecule modulator of spliceosome complex and has been shown to lower leukemia burden in SRSF2-P95H mutant mice. This review focuses on the incidence of mutant SRSF2 across various MMOS as well as recent clinical development of spliceosome inhibitors.