Low rate of calreticulin mutations in refractory anaemia with ring sideroblasts and marked thrombocytosis

Predicting survival in patients with myelodysplastic/myeloproliferative neoplasms with SF3B1 mutation and thrombocytosis

We investigated data from 180 consecutive patients with myelodysplastic/myeloproliferative neoplasms with SF3B1 mutation and thrombocytosis (MDS/MPN-SF3B1-T) who were diagnosed according to the 2022 World Health Organization (WHO) classification of myeloid neoplasms to identify covariates associated with survival. At a median follow-up of 48 months (95% confidence interval [CI] 35-61 months), the median survival was 69 months (95% CI 59-79 months). Patients with bone marrow ring sideroblasts (RS) < 15% had shorter median overall survival (OS) than did those with bone marrow RS ≥ 15% (41 months [95% CI 32-50 months] versus 76 months [95% CI 59-93 months]; P < 0.001). According to the univariable analyses of OS, age ≥ 65 years (P < 0.001), hemoglobin concentration (Hb) < 80 g/L (P = 0.090), platelet count (PLT) ≥ 800 × 10E + 9/L (P = 0.087), bone marrow RS < 15% (P < 0.001), the Revised International Prognostic Scoring System (IPSS-R) cytogenetic category intermediate/poor/very poor (P = 0.005), SETBP1 mutation (P = 0.061) and SRSF2 mutation (P < 0.001) were associated with poor survival. Based on variables selected from univariable analyses, two separate survival prediction models, a clinical survival model, and a clinical-molecular survival model, were developed using multivariable analyses with the minimum value of the Akaike information criterion (AIC) to specifically predict outcomes in patients with MDS/MPN-SF3B1-T according to the 2022 WHO classification.

Myelodysplastic Syndrome: Clinical Characteristics and Significance of Preclinically Detecting Biallelic Mutations in the TET2 Gene

Myelodysplastic syndrome (MDS) is a clonal disease derived from hematopoietic stem cells, characterized by ineffective hematopoiesis (resulting in peripheral blood cytopenia) and an increased risk of transformation into acute myeloid leukemia. MDS is caused by a complex combination of genetic mutations resulting in a heterogeneous genotype. Genetic studies have identified a set of aberrations that play a central role in the pathogenesis of MDS. In this article, we present a clinical case of MDS transformation into acute myeloid leukemia in the context of two cell lines exhibiting morphological, immunophenotypic, and dysmyelopoiesis markers and the presence of two heterozygous mutations in the TET2 gene.

Essential thrombocythemia: 2024 update on diagnosis, risk stratification, and management

OVERVIEW

Essential thrombocythemia is a Janus kinase 2 (JAK2) mutation-prevalent myeloproliferative neoplasm characterized by clonal thrombocytosis; clinical course is often indolent but might be interrupted by thrombotic or hemorrhagic complications, microcirculatory symptoms (e.g., headaches, lightheadedness, and acral paresthesias), and, less frequently, by disease transformation into myelofibrosis (MF) or acute myeloid leukemia.

DIAGNOSIS

In addition to thrombocytosis (platelets ≥450 × 109 /L), formal diagnosis requires the exclusion of other myeloid neoplasms, including prefibrotic MF, polycythemia vera, chronic myeloid leukemia, and myelodysplastic syndromes with ring sideroblasts and thrombocytosis. Bone marrow morphology typically shows increased number of mature-appearing megakaryocytes distributed in loose clusters.

GENETICS

Approximately 80% of patients express myeloproliferative neoplasm driver mutations (JAK2, CALR, MPL), in a mutually exclusive manner; in addition, about 50% harbor other mutations, the most frequent being TET2 (9%-11%), ASXL1 (7%-20%), DNMT3A (7%), and SF3B1 (5%). Abnormal karyotype is seen in <10% of patients and includes +9/20q-/13q-.

SURVIVAL AND PROGNOSIS

Life expectancy is less than that of the control population. Median survival is approximately 18 years but exceeds >35 years in younger patients. The triple A survival risk model, based on Age, Absolute neutrophil count, and Absolute lymphocyte count, effectively delineates high-, intermediate-1-, intermediate-2-, and low-risk disease with corresponding median survivals of 8, 14, 21, and 47 years.

RISK FACTORS FOR THROMBOSIS

Four risk categories are considered: very low (age ≤60 years, no thrombosis history, JAK2 wild-type), low (same as very low but JAK2 mutation present), intermediate (same as low but age >60 years), and high (thrombosis history or age >60 years with JAK2 mutation).

MUTATIONS AND PROGNOSIS

MPL and CALR-1 mutations have been associated with increased risk of MF transformation; spliceosome with inferior overall and MF-free survival; TP53 with leukemic transformation, and JAK2V617F with thrombosis. Leukemic transformation rate at 10 years is <1% but might be higher in JAK2-mutated patients with extreme thrombocytosis and those with abnormal karyotype.

TREATMENT

The main goal of therapy is to prevent thrombosis. In this regard, once-daily low-dose aspirin is advised for all patients and twice daily for low-risk disease. Cytoreductive therapy is advised for high-risk and optional for intermediate-risk disease. First-line cytoreductive drugs of choice are hydroxyurea and pegylated interferon-α and second-line busulfan.

ADDITIONAL CONTENT

The current review includes specific treatment strategies in the context of extreme thrombocytosis, pregnancy, splanchnic vein thrombosis, perioperative care, and post-essential thrombocythemia MF, as well as new investigational drugs.

JAK2, CALR, and MPL Mutation Profiles in Colombian patients with BCR-ABL Negative Myeloproliferative Neoplasms

Background

Among the chronic myeloproliferative neoplasms (MPNs) not associated with BCR-ABL mutations are polycythemia vera, primary myelofibrosis, and essential thrombocythemia. These diseases are caused by mutations in genes, such as the JAK2, MPL, and CALR genes, which participate in regulating the JAK-STAT signaling pathway.

Objective

This study aimed to establish the frequencies of mutations in the JAK2, MPL, and CALR genes in a group of Colombian patients with a negative clinical diagnosis of BCR-ABL chronic myeloproliferative neoplasms.

Methods

The JAK2 V617F and MPL W515K mutations and deletions or insertions in exon 9 of the CALR gene were analyzed in 52 Colombian patients with polycythemia vera, primary myelofibrosis, and essential thrombocythemia.

Results

The JAK2V617F mutation was carried by 51.9% of the patients, the CALR mutation by 23%, and the MPL mutation by 3.8%; 23% were triple-negative for the mutations analyzed. In these neoplasms, 6 mutation types in CALR were identified, one of which has not been previously reported. Additionally, one patient presented a double mutation in both the CALR and JAK2 genes. Regarding the hematological results for the mutations, significant differences were found in the hemoglobin level, hematocrit level, and platelet count among the three neoplasms.

Conclusion

Thus, this study demonstrates the importance of the molecular characterization of the JAK2, CALR and MPL mutations in Colombian patients (the genetic context of which remains unclear in the abovementioned neoplasms) to achieve an accurate diagnosis, a good prognosis, adequate management, and patient survival.

Many faces of SF3B1-mutated myeloid neoplasms: concurrent mutational profiles contribute to the diverse clinical and morphologic features

Splicing factor SF3B1 mutation occurs in 20-30% of myelodysplastic syndrome (MDS) and myelodysplasia/myeloproliferative neoplasm (MDS/MPN), particularly those with ring sideroblasts (RS), and rarely in acute myeloid leukemia (AML). In this study, we performed a comprehensive evaluation of 77 SF3B1-mutated myeloid neoplasms (45 MDS, 18 MDS/MPN, 13 AML, and 1 MPN), including their clinical presentations, morphologic features, cytogenetic studies, and targeted next-generation sequencing. Our study demonstrated that concurrent gene mutations were very different in SF3B1-mutated MDS, MDS/MPN, and AML. MDS cases were frequently characterized by either sole SF3B1 mutation or in combination with TET2 mutation. Acquiring additional mutations in transcription factors, such as RUNX1 and GATA2, were associated with increased blasts and progression to AML in patients with MDS or MDS/MPN. Our study also demonstrated that SF3B1-mutated MDS/MPN was not only associated with thrombocytosis (5/18, 27.7%), defined by the current WHO classification as MDS/MPN-RS-T, but also associated with neutrophilia (6/18, 33.3%), monocytosis (6/18, 33.3%), and mastocytosis (1/18, 5.6%). Our results indicate that although SF3B1-mutated myeloid neoplasms in general have a good prognosis, evaluation of the concurrent gene mutational profile is important for risk stratification. In addition, our study, in combination with other published data, suggests that the category of MDS/MPN-RS-T in the current WHO classification could be expanded to include SF3B1-mutated MDS/MPN-RS with peripheral leukocytosis such as neutrophilia and monocytosis.

Causes and Pathophysiology of Acquired Sideroblastic Anemia

The sideroblastic anemias are a heterogeneous group of inherited and acquired disorders characterized by anemia and the presence of ring sideroblasts in the bone marrow. Ring sideroblasts are abnormal erythroblasts with iron-loaded mitochondria that are visualized by Prussian blue staining as a perinuclear ring of green-blue granules. The mechanisms that lead to the ring sideroblast formation are heterogeneous, but in all of them, there is an abnormal deposition of iron in the mitochondria of erythroblasts. Congenital sideroblastic anemias include nonsyndromic and syndromic disorders. Acquired sideroblastic anemias include conditions that range from clonal disorders (myeloid neoplasms as myelodysplastic syndromes and myelodysplastic/myeloproliferative neoplasms with ring sideroblasts) to toxic or metabolic reversible sideroblastic anemia. In the last 30 years, due to the advances in genomic techniques, a deep knowledge of the pathophysiological mechanisms has been accomplished and the bases for possible targeted treatments have been established. The distinction between the different forms of sideroblastic anemia is based on the study of the characteristics of the anemia, age of diagnosis, clinical manifestations, and the performance of laboratory analysis involving genetic testing in many cases. This review focuses on the differential diagnosis of acquired disorders associated with ring sideroblasts.

Molecular landscape and clonal architecture of adult myelodysplastic/myeloproliferative neoplasms

More than 90% of patients with myelodysplastic/myeloproliferative neoplasms (MDSs/MPNs) harbor somatic mutations in myeloid-related genes, but still, current diagnostic criteria do not include molecular data. We performed genome-wide sequencing techniques to characterize the mutational landscape of a large and clinically well-characterized cohort including 367 adults with MDS/MPN subtypes, including chronic myelomonocytic leukemia (CMML; n = 119), atypical chronic myeloid leukemia (aCML; n = 71), MDS/MPN with ring sideroblasts and thrombocytosis (MDS/MPN-RS-T; n = 71), and MDS/MPN unclassifiable (MDS/MPN-U; n = 106). A total of 30 genes were recurrently mutated in ≥3% of the cohort. Distribution of recurrently mutated genes and clonal architecture differed among MDS/MPN subtypes. Statistical analysis revealed significant correlations between recurrently mutated genes, as well as genotype-phenotype associations. We identified specific gene combinations that were associated with distinct MDS/MPN subtypes and that were mutually exclusive with most of the other MDSs/MPNs (eg, TET2-SRSF2 in CMML, ASXL1-SETBP1 in aCML, and SF3B1-JAK2 in MDS/MPN-RS-T). Patients with MDS/MPN-U were the most heterogeneous and displayed different molecular profiles that mimicked the ones observed in other MDS/MPN subtypes and that had an impact on the outcome of the patients. Specific gene mutations also had an impact on the outcome of the different MDS/MPN subtypes, which may be relevant for clinical decision-making. Overall, the results of this study help to elucidate the heterogeneity found in these neoplasms, which can be of use in the clinical setting of MDS/MPN.

Genetic Aspects of Myelodysplastic/Myeloproliferative Neoplasms

Simple Summary

Myelodysplastic/myeloproliferative neoplasms (MDS/MPN) are clonal myeloid neoplasms characterized, at the time of their presentation, by the simultaneous presence of both myelodysplastic and myeloproliferative features. In MDS/MPN, the karyotype is often normal but mutations in genes that are common across myeloid neoplasms can be detected in a high proportion of cases by targeted sequencing. In this review, we intend to summarize the main genetic findings across all MDS/MPN overlap syndromes and discuss their relevance in the management of patients.

Abstract

Myelodysplastic/myeloproliferative neoplasms (MDS/MPN) are myeloid neoplasms characterized by the presentation of overlapping features from both myelodysplastic syndromes and myeloproliferative neoplasms. Although the classification of MDS/MPN relies largely on clinical features and peripheral blood and bone marrow morphology, studies have demonstrated that a large proportion of patients (~90%) with this disease harbor somatic mutations in a group of genes that are common across myeloid neoplasms. These mutations play a role in the clinical heterogeneity of these diseases and their clinical evolution. Nevertheless, none of them is specific to MDS/MPN and current diagnostic criteria do not include molecular data. Even when such alterations can be helpful for differential diagnosis, they should not be used alone as proof of neoplasia because some of these mutations may also occur in healthy older people. Here, we intend to review the main genetic findings across all MDS/MPN overlap syndromes and discuss their relevance in the management of the patients.

The Contemporary Approach to CALR-Positive Myeloproliferative Neoplasms

CALR mutations are a revolutionary discovery and represent an important hallmark of myeloproliferative neoplasms (MPN), especially essential thrombocythemia and primary myelofibrosis. To date, several CALR mutations were identified, with only frameshift mutations linked to the diseased phenotype. It is of diagnostic and prognostic importance to properly define the type of CALR mutation and subclassify it according to its structural similarities to the classical mutations, a 52-bp deletion (type 1 mutation) and a 5-bp insertion (type 2 mutation), using a statistical approximation algorithm (AGADIR). Today, the knowledge on the pathogenesis of CALR-positive MPN is expanding and several cellular mechanisms have been recognized that finally cause a clonal hematopoietic expansion. In this review, we discuss the current basis of the cellular effects of CALR mutants and the understanding of its implementation in the current diagnostic laboratorial and medical practice. Different methods of CALR detection are explained and a diagnostic algorithm is shown that aids in the approach to CALR-positive MPN. Finally, contemporary methods joining artificial intelligence in accordance with molecular-genetic biomarkers in the approach to MPN are presented.

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.

The Essential Thrombocythemia in 2020: What We Know and Where We Still Have to Dig Deep

The Essential Thrombocythemia is a Chronic Philadelphia-negative Myeloproliferative Neoplasm characterized by a survival curve that is only slightly worse than that of age- and sex-adjusted healthy population. The criteria for diagnosis were reviewed in 2016 by WHO. The incidence varies from 0.2 to 2.5:100 000 people per year, with a prevalence of 38 to 57 cases per 100 000 people. The main characteristics of ET are the marked thrombocytosis and the high frequency of thrombosis. The spectrum of symptoms is quite wide, but fatigue results to be the most frequent. Thrombosis is frequently observed, often occurring before or at the time of diagnosis. The classification of thrombotic risk has undergone several revisions. Recently, the revised-IPSET-t has distinguished 4 risk classes, from very low risk to high risk. Driver mutations seem to influence thrombotic risk and prognosis, while the role of sub-driver mutations still remains uncertain. Antiplatelet therapy is recommended in all patients aged ⩾ 60 years and in those with a positive history of thrombosis or with cardiovascular risk factors, while cytoreductive therapy with hydroxyurea or interferon is reserved for high-risk patients.

Efficacy of lenalidomide in myelodysplastic/myeloproliferative neoplasms with ring sideroblasts and an extreme platelet count

Lenalidomide is efficient in reducing red blood cell transfusion dependency and markedly lowering platelet counts in MDS/MPN-RS-T in the context of major platelet counts.

Myelodysplastic Syndrome/Myeloproliferative Neoplasm with Ring Sideroblasts and Thrombocytosis with Cooccurrent SF3B1 and MPL Gene Mutations: A Case Report and Brief Review of the Literature

BACKGROUND

Myelodysplastic syndrome/myeloproliferative neoplasm with ring sideroblasts and thrombocytosis (MDS/MPN-RS-T) is a new disease entity in the current WHO classification. Genetically, 60%-90% of cases have mutations in SF3B1, strongly associated with RS, and more than half of them cooccur with JAK2 V617F. This report describes the rare case of MDS/MPN-RS-T with SF3B1 mutation cooccurring with an MPL mutation.

METHODS

We report a 79-year-old man who was referred because of generalized edema. Peripheral blood testing showed macrocytic anemia and thrombocytosis, and bone marrow analysis demonstrated dyserythropoiesis with RS and increased megakaryocytes. A molecular study was performed to detect SF3B1 mutations and recurrent mutations in MPN disease (JAK2 V617F/exon 12, CALR gene exon 9, and MPL gene exon 10 mutations).

RESULTS

The molecular study revealed SF3B1 K666T and MPL W515R mutations, while BCR-ABL1 or JAK2 V617F/exon 12 and CALR mutations were all negative.

CONCLUSION

This is a rare case of concomitant SF3B1 and MPL mutations in MDS/MPN-RS-T.

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.

Refractory anemia with ring sideroblasts (RARS) and RARS with thrombocytosis: "2019 Update on Diagnosis, Risk-stratification, and Management"

DISEASE OVERVIEW

Ring sideroblasts (RS) are erythroid precursors with abnormal perinuclear mitochondrial iron accumulation. Two myeloid neoplasms defined by the presence of RS, include refractory anemia with ring sideroblasts (RARS), now classified under myelodysplastic syndromes with RS (MDS-RS) and RARS with thrombocytosis (RARS-T); now called myelodysplastic/myeloproliferative neoplasm with RS and thrombocytosis (MDS/MPN-RS-T).

DIAGNOSIS

MDS-RS is a lower-risk MDS, with single or multilineage dysplasia (SLD/MLD), <5% bone marrow (BM) blasts and ≥ 15% BM RS (≥5% in the presence of SF3B1 mutations). MDS/MPN-RS-T, now a formal entity in the MDS/MPN overlap syndromes, has diagnostic features of MDS-RS-SLD, along with a platelet count ≥450 × 10(9)/L and large atypical megakaryocytes.

MUTATIONS AND KARYOTYPE

Mutations in SF3B1 are seen in ≥80% of patients with MDS-RS-SLD and MDS/MPN-RS-T, and strongly correlate with the presence of BM RS; MDS/MPN-RS-T patients also demonstrate JAK2V617F, ASXL1, DNMT3A, SETBP1, and TET2 mutations. Cytogenetic abnormalities are uncommon in both.

RISK STRATIFICATION

Most patients with MDS-RS-SLD are stratified into lower-risk groups by the revised-IPSS. Disease outcome in MDS/MPN-RS-T is better than that of MDS-RS-SLD, but worse than that of essential thrombocythemia. Both diseases have a low risk of leukemic transformation.

TREATMENT

Anemia and iron overload are complications seen in both and are managed similar to lower-risk MDS and MPN. The advent of luspatercept, a first-in-class erythroid maturation agent will tremendously boost the ability to manage anemia. Aspirin therapy is reasonable in MDS/MPN-RS-T, especially in the presence of JAK2V617F, but the value of platelet-lowering drugs remains uncertain.

Revisiting diagnostic criteria for myelodysplastic/myeloproliferative neoplasms with ring sideroblasts and thrombocytosis: Borderline cases without anemia exist

INTRODUCTION

Myelodysplastic/myeloproliferative neoplasm with ring sideroblasts and thrombocytosis (MDS/MPN-RS-T) is a rare disease in the 2016 revised World Health Organization (WHO) classification. Diagnostic criteria include the following: persistent thrombocytosis (>450 × 10⁹ /L) with clustering of atypical megakaryocytes, refractory anemia, dyserythropoiesis with ring sideroblasts, and the presence of the spliceosome factor 3b subunit (SF3B1) mutation. It is unclear if anemia should be a required criterion for this diagnosis as cases which show all other features of MDS/MPN-RS-T but without anemia exist.

METHODS

We searched for borderline cases of MDS/MPN-RS-T in which refractory anemia was absent at diagnosis in two major academic institutes.

RESULTS

Three cases without anemia were identified. These cases all showed other classic morphologic and clinical features of MDS/MPN-RS-T, including thrombocytosis, atypical megakaryocytes with clustering, and characteristic SF3B1 and JAK2 V617F mutations.

CONCLUSION

Given these findings, the requirement of refractory anemia as a diagnostic criterion for MDS/MPN-RS-T should be re-evaluated. Removal of refractory anemia as a diagnostic criterion would incorporate current borderline cases and extend the spectrum of this disorder.

Challenges in Myelodysplastic/Myeloproliferative Neoplasms (MDS/MPN)

Myelodysplastic/myeloproliferative neoplasms (MDS/MPN) are hybrid group of chronic myeloid neoplasms combining features of both MDS and MPN. The World Health Organization classification coined this group designation in 2008 to include chronic myelomonocytic leukemia, atypical chronic myeloid leukemia, juvenile myelomoncoytic leukemia, refractory anemia with ring sideroblasts and thrombocytosis as a provisional entity, and MDS/MPN unclassified. In this review, we highlight the challenges in diagnosing this group of the diseases, summarize the updates in classification, and discuss recent evolving understanding of the genetic landscape. We review risk-stratification models and overview the current management largely adapted from current MDS or MPN therapies. We define clinical benefit of therapy based on new proposed response criteria developed specifically for these groups of neoplasms. Finally, we introduce future opportunities including the planned international ABN MARRO (A Novel therapy combinations in untreated MDS/MPN And Relapsed/Refractory Overlap Syndromes) clinical study led by the MDS/MPN International Working Group.

Diagnostic, Prognostic, and Predictive Utility of Recurrent Somatic Mutations in Myeloid Neoplasms

The classification and risk stratification of myeloid neoplasms, including acute myeloid leukemia, myelodysplastic syndromes, myelodysplastic syndromes/myeloproliferative neoplasms, and myeloproliferative neoplasms, have increasingly been guided by molecular genetic abnormalities. Gene expression analysis and next-generation sequencing have led to the ever increasing discovery of somatic gene mutations in myeloid neoplasms. Mutations have been identified in genes involved in epigenetic modification, RNA splicing, transcription factors, DNA repair, and the cohesin complex. These new somatic/acquired gene mutations have refined the classification of myeloid neoplasms and have been incorporated into the 2016 update of the World Health Organization (WHO) classification and the National Comprehensive Cancer Network guidelines. They have also been helpful in the development of new targeted therapeutic agents. In the present review, we describe the clinical utility of recently identified, clinically important gene mutations in myeloid neoplasms, including those incorporated in the 2016 update of the WHO classification.

An Exercise in Extrapolation: Clinical Management of Atypical CML, MDS/MPN-Unclassifiable, and MDS/MPN-RS-T

According to the recently published 2016 World Health Organization (WHO) classification of myeloid malignancies, myelodysplastic/myeloproliferative neoplasms (MDS/MPN) include atypical chronic myeloid leukemia (aCML), MDS/MPN-unclassifiable (MDS/MPN-U), chronic myelomonocytic leukemia (CMML), juvenile myelomonocytic leukemia (JMML), and MDS/MPN ring sideroblasts with thrombocytosis (MDS/MPN-RS-T). MDS/MPN-RS-T was previously a provisional category known as refractory anemia with ring sideroblasts with thrombocytosis (RARS-T) which has now attained a distinct designation in the 2016 WHO classification. In this review, we focus on biology and management of aCML, MDS/MPN-U, and MDS/MPN-RS-T. There is considerable overlap between these entities which we attempt to further elucidate in this review. We also discuss recent advances in the field of molecular landscape that further defines and characterizes this heterogeneous group of disorders. The paucity of clinical trials available secondary to unclear pathogenesis and rarity of these diseases makes the management of these entities clinically challenging. This review summarizes some of the current knowledge of the molecular pathogenesis and suggested treatment guidelines based on the available data.

Turning the tide in myelodysplastic/myeloproliferative neoplasms

Myelodysplastic syndromes/myeloproliferative neoplasms (MDS/MPN) are aggressive myeloid malignancies recognized as a distinct category owing to their unique combination of dysplastic and proliferative features. Although current classification schemes still emphasize morphology and exclusionary criteria, disease-defining somatic mutations and/or germline predisposition alleles are increasingly incorporated into diagnostic algorithms. The developing picture suggests that phenotypes are driven mostly by epigenetic mechanisms that reflect a complex interplay between genotype, physiological processes such as ageing and interactions between malignant haematopoietic cells and the stromal microenvironment of the bone marrow. Despite the rapid accumulation of genetic knowledge, therapies have remained nonspecific and largely inefficient. In this Review, we discuss the pathogenesis of MDS/MPN, focusing on the relationship between genotype and phenotype and the molecular underpinnings of epigenetic dysregulation. Starting with the limitations of current therapies, we also explore how the available mechanistic data may be harnessed to inform strategies to develop rational and more effective treatments, and which gaps in our knowledge need to be filled to translate biological understanding into clinical progress.

Splicing factor mutations in MDS RARS and MDS/MPN-RS-T

Spliceosomal mutations, especially mutations in SF3B1, are frequently (>80%) identified in patients with refractory anemia with ringed sideroblasts (RARS) and myelodysplastic/myeloproliferative neoplasms with ringed sideroblasts and thrombocytosis (MDS/MPN-RS-T; previously known as RARS-T), and SF3B1 mutations have a high positive predictive value for disease phenotype with ringed sideroblasts. These observations suggest that SF3B1 mutations play important roles in the pathogenesis of these disorders and formation of ringed sideroblasts. Here we will review recent insights into the molecular mechanisms of mis-splicing caused by mutant SF3B1 and the pathogenesis of RSs in the context of congenital sideroblastic anemia as well as RARS with SF3B1 mutations. We will also discuss therapy of SF3B1 mutant MDS, including novel approaches.

Treatment of Refractory Anemia with Ring Sideroblasts Associated with Marked Thrombocytosis with Lenalidomide in a Patient Testing Negative for 5q Deletion and JAK2 V617F and MPL W515K/L Mutations

Refractory anemia with ring sideroblasts associated with marked thrombocytosis (RARS-T) is a hematologic malignancy that often results in transfusion dependency and a hypercoagulable state. This rare disease currently lacks formal guidelines for treatment; however, various case reports have demonstrated efficacy in the use of lenalidomide. This immunomodulatory drug has shown promise in patients with 5q deletions, with reports of achieving transfusion independence and normalization of platelet counts. Herein we present the case of a 68-year-old African American woman with RARS-T who tested negative for 5q deletion and JAK2 V617F and MPL W515K/L mutations. Her treatment with lenalidomide therapy resulted in a five-year durable complete clinical response.

Differential Dynamics of CALR Mutant Allele Burden in Myeloproliferative Neoplasms during Interferon Alfa Treatment

Discovery of somatic mutations in the calreticulin gene (CALR) has identified a subgroup of Philadelphia-negative chronic myeloproliferative neoplasms (MPN) with separate haematological characteristics and prognosis. CALR mutations serve as novel markers both of diagnostic value and as targets for monitoring molecular responses during therapy. Interferon-α (IFN) selectively targets the malignant clone in a subset of MPN patients and can induce both haematological and molecular remissions in CALR mutated essential thrombocythemia (ET) patients. We investigated the response to IFN in a cohort of 21 CALR mutated MPN patients including ET, prefibrotic primary myelofibrosis (pre-PMF), and primary myelofibrosis (PMF) with a median follow-up of 31 months. For evaluation of a molecular response, we developed highly sensitive quantitative PCR (qPCR) assays for monitoring the mutant allele burden of the two most prevalent CALR mutations (type 1 and type 2). Thirteen patients (62%) experienced a decrease in the mutant allele burden with a median decline of 29% from baseline. However, only four patients, including patients with ET, pre-PMF, and PMF diagnosis, achieved molecular responder (MR) status with >50% reduction in mutant allele burden according to European LeukemiaNet (ELN) guidelines. MR patients displayed significant differences in the dynamics of the CALR mutant load with regard to time to response and dynamics in mutant allele burden after discontinuation of IFN treatment. Furthermore, we highlight the prognostic value of the CALR mutant allele burden by showing a close association with leucocyte- and platelet counts, hemoglobin concentration, in addition to plasma lactate dehydrogenase (LDH) irrespective of molecular response and treatment status.

Coexistence of lymphoproliferative and myeloproliferative neoplasms with simultaneous CALR and JAK2 V617F mutations

BACKGROUND

Hematopoietic malignancies are a group of blood cell disorders characterized by abnormal hematopoietic proliferation.

OBJECTIVE

The identification of specific clinicopathologic characteristics and tumor-related gene status provides critical information on potential therapeutic targets.

METHODS

The specimens were tested with immunohistochemistry, flow cytometry, RT-PCR and fragment analysis.

RESULTS

In this study, a patient with a long history of tobacco use was reported with a diagnosis of simultaneous low-grade B-cell lymphoproliferative disorder (LPD) and myeloproliferative neoplasm (MPN). Mutational analysis revealed that JAK2 V617F mutation and CALR mutation with 52bp deletion were present in this patient.

CONCLUSION

These results suggest that lymphoproliferative and myeloproliferative neoplasms may coexist, although the pathogenetic mechanism of coexisting hematologic requires further investigation. Additionally, the data indicate that JAK2 V617F and CALR mutations are not mutually exclusive and the actual frequency of simultaneous JAK2 V617F and CALR mutations is unknown. Whether the coexistence of these mutations imposes any biological or clinical significance awaits further investigation.

Predictors of survival in refractory anemia with ring sideroblasts and thrombocytosis (RARS-T) and the role of next-generation sequencing

Refractory anemia with ring sideroblasts and thrombocytosis (RARS-T) shares overlapping features of myelodysplastic syndromes (MDS) and myeloproliferative neoplasms (MPN). RARS-T is characterized by SF3B1 and JAK2 mutations and prognosis is considered to be better than MDS but not as good as MPN. The objective of the study was to identify predictors of survival in RARS-T. We analyzed clinical and laboratory variables in 82 patients and applied a 27-gene NGS assay to 48 marrow samples obtained at diagnosis. 94% of patients had ≥1 mutations; common mutations being: SF3B1 85%, JAK2V617F 33%, ASXL1 29%, DNMT3A 13%, SETBP1 13% and TET2 10%. In a multivariable survival analysis (n = 82), anemia (P = 0.02) [HB< 10 gm/dl: HR 2.3, 95% CI 1.2-4.6] and abnormal karyotype (P =.01) [HR 6.1, 95% CI 2.7-13.8] were independently prognostic for inferior survival. In patients with NGS information (n = 48), univariate analysis showed association between poor survival and presence of SETBP1 (P = 0.04) or ASXL1 (P = 0.08) mutations whereas the absence of these mutations (ASXL1wt/SETBP1wt) was favorable (P = 0.04); the number of concurrent mutations did not provide additional prognostication (P = 0.3). We developed a HR-weighted prognostic model, with 2 points for an abnormal karyotype, 1 point for either ASXL1 and/or SETBP1 mutations, and 1 point for a HB level < 10 gm/dl, which effectively stratified patients into three risk categories; low (0 points), intermediate (1 point) and high (≥2 points), with median survivals of 80, 42 and 11 months respectively (P = 0.01). In summary, we confirm the unique mutational landscape in RARS-T and provide a novel mutation-enhanced prognostic model.

Coexisting JAK2V617F and CALR Exon 9 Mutation in Essential Thrombocythemia

Classic "BCR-ABL1-negative" MPN is an operational sub-category of MPN that includes polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF) harboring JAK2V617F as the most common mutation. JAK2V617F can be detected in about 95 % of patients with PV while remaining 5 % of PV patients carry a somatic mutation of JAK2 exon 12. Approximately one-third of patients with ET or PMF do not carry any mutation in JAK2 or MPL. In December 2013, mutations were described in calreticulin (CALR) gene in 67-71 and 56-88 % of JAK2V617F and MPL negative patients with ET and PMF, respectively. Since this discovery CALR mutations have been reported to be mutually exclusive with JAK2V617F or MPL mutations. However recently few studies (eleven published reports) reported the coexistence of JAK2V617F and CALR in MPN. In the present study we are reporting JAK2V617F positive ET patient from our center with coexisting CALR exon 9 mutation type c.1214_1225del12 (p.E405_D408del) that was never reported before as a coexisting mutation and describing in detail the clinical outcomes.

Genomic landscape of megakaryopoiesis and platelet function defects

Megakaryopoiesis is a complex, stepwise process that takes place largely in the bone marrow. At the apex of the hierarchy, hematopoietic stem cells undergo a number of lineage commitment decisions that ultimately lead to the production of polyploid megakaryocytes. On average, megakaryocytes release 10(11) platelets per day into the blood that repair vascular injuries and prevent excessive bleeding. This differentiation process is tightly controlled by exogenous and endogenous factors, which have been the topics of intense research in the hematopoietic field. Indeed, a skewing of megakaryocyte commitment and differentiation may entail the onset of myeloproliferative neoplasms and other preleukemic disorders together with acute megakaryoblastic leukemia, whereas quantitative or qualitative defects in platelet production can lead to inherited platelet disorders. The recent advent of next-generation sequencing has prompted mapping of the genomic landscape of these conditions to provide an accurate view of the underlying lesions. The aims of this review are to introduce the physiological pathways of megakaryopoiesis and to present landmark studies on acquired and inherited disorders that target them. These studies have not only introduced a new era in the fields of molecular medicine and targeted therapies but may also provide us with a better understanding of the mechanisms underlying normal megakaryopoiesis and thrombopoiesis that can inform efforts to create alternative sources of megakaryocytes and platelets.

Calreticulin (CALR) mutation in myeloproliferative neoplasms (MPNs)

As a heterogeneous group of disease, myeloproliferative neoplasms (MPNs) have confused hematologists and hematopathologists with their protean clinical presentations and myriads of morphologies. A thought of classifying MPNs based on molecular alterations has gained popularity because there is increasing evidence that molecular or chromosomal alterations have a better correlation with clinical presentation, response to therapies, and prognosis than conventional morphological classification. This type of efforts has been facilitated by the advancement of molecular technologies. A significant number of gene mutations have been identified in MPNs with JAK2 and MPL being the major ones. However, a significant gap is present in that many cases of MPNs do not harbor any of these mutations. This gap is recently filled by the discovery of Calreticulin (CALR) mutation in MPNs without JAK2 or MPL mutation and since then, the clinical and molecular correlation in MPNs has become a hot research topic. There seems to be a fairly consistent correlation between CALR mutation and certain hematological parameters such as a high platelet count and a better prognosis in MPNs with CALR mutation. However, controversies are present regarding the risks of thrombosis, interactions of CALR with other gene mutation, the role of CALR in the pathogenesis, and the optimal treatment strategies. In addition, there are many questions remain to be answered, which all boiled down to the molecular mechanisms by which CALR causes or contributes to MPNs. Here, we summarized current published literatures on CALR mutations in MPNs with an emphasis on the clinical-molecular correlation. We also discussed the controversies and questions remain to be answered.

CALR mutations screening in wild type JAK2(V617F) and MPL(W515K/L) Brazilian myeloproliferative neoplasm patients

Some myeloproliferative neoplasm (MPN) patients harbor JAK2(V617F) mutation, and CALR mutations were recently discovered in wild type (WT) JAK2(V617F). We evaluated the frequency and type of CALR mutations, and clinical and hematological characteristics in WT JAK2(V617F) and MPL(W515K/L) MPN patients. Sixty-five patients were included: 21 with primary myelofibrosis (PMF), 21 with myelofibrosis post-essential thrombocythemia (MPET) and 23 with essential thrombocythemia (ET). Screening for JAK2(V617F) and MPL(W515K/L) were performed using real-time PCR, while CALR mutations were analyzed by fragment analysis and Sanger sequencing. JAK2(V617F) was the most frequent mutation (54.5%) and one patient (1.5%) harbored MPL(W515L). CALR mutations were present in 38.1% of PMF, 12.5% of ET and 33.3% of MPET patients. Five types of CALR mutations were detected, among which type 1 (32.1%) and type 2 (21.4%) were found to be the most common. A novel CALR mutation in a PMF patient was found. Patients carrying CALR mutations had higher platelet count and less presence of splenomegaly than JAK2(V617F), while triple negatives had higher C-reactive protein levels than CALR mutant carriers. Screening for CALR mutations and its correlation with clinical features could be useful for the characterization of MPN patients and result in its incorporation into a new prognostic score.

Refractory anemia with ring sideroblasts and RARS with thrombocytosis

DISEASE OVERVIEW

Ring sideroblasts (RS) are erythroid precursors with abnormal perinuclear mitochondrial iron accumulation. Two myeloid neoplasms defined by the presence of RS, include refractory anemia with ring sideroblasts (RARS) and RARS with thrombocytosis (RARS-T).

DIAGNOSIS

RARS is a lower risk myelodysplastic syndrome (MDS) with dysplasia limited to the erythroid lineage, <5% bone marrow (BM) blasts and ≥15% BM RS. RARS-T is a provisional entity in the MDS/MPN (myeloproliferative neoplasm) overlap syndromes, with diagnostic features of RARS, along with a platelet count ≥450 × 10(9)/L and large atypical megakaryocytes similar to those observed in BCR-ABL1 negative MPN. Mutations and Karyotype: Mutations in the SF3B1 gene are seen in ≥80% of patients with RARS and RARS-T, and strongly correlate with the presence of BM RS; RARS-T patients have additional mutations such as, JAK2V617F (∼60%), MPL (<5%), and CALR (<5%). Cytogenetic abnormalities are uncommon in both RARS and RARS-T.

RISK STRATIFICATION

Most patients with RARS are stratified into lower risk groups by the International Prognostic Scoring System (IPSS) for MDS and the revised IPSS. Disease outcome in RARS-T is better than that of RARS, but worse than that of essential thrombocytosis. Both RARS and RARS-T have a low risk of leukemic transformation.

TREATMENT

Anemia and iron overload are complications in both diseases and are managed similar to lower risk MDS. Aspirin therapy is reasonable in RARS-T, especially in the presence of JAK2V617F, but the value of platelet-lowering drugs is uncertain. Case reports of RARS-T therapy with lenalidomide warrant additional studies.

Molecular diagnostics of myeloproliferative neoplasms

Since the discovery of the JAK2 V617F mutation in the majority of the myeloproliferative neoplasms (MPN) of polycythemia vera, essential thrombocythemia and primary myelofibrosis ten years ago, further MPN-specific mutational events, notably in JAK2 exon 12, MPL exon 10 and CALR exon 9 have been identified. These discoveries have been rapidly incorporated into evolving molecular diagnostic algorithms. Whilst many of these mutations appear to have prognostic implications, establishing MPN diagnosis is of immediate clinical importance with selection, implementation and the continual evaluation of the appropriate laboratory methodology to achieve this diagnosis similarly vital. The advantages and limitations of these approaches in identifying and quantitating the common MPN-associated mutations are considered herein with particular regard to their clinical utility. The evolution of molecular diagnostic applications and platforms has occurred in parallel with the discovery of MPN-associated mutations, and it therefore appears likely that emerging technologies such as next-generation sequencing and digital PCR will in the future play an increasing role in the molecular diagnosis of MPN.

Analysis of phenotype and outcome in essential thrombocythemia with CALR or JAK2 mutations

The JAK2 V617F mutation, the thrombopoietin receptor MPL W515K/L mutation and calreticulin (CALR) mutations are mutually exclusive in essential thrombocythemia and support a novel molecular categorization of essential thrombocythemia. CALR mutations account for approximately 30% of cases of essential thrombocythemia. In a retrospective study, we examined the frequency of MPL and CALR mutations in JAK2 V617F-negative cases of essential thrombocythemia (n=103). In addition, we compared the clinical phenotype and outcome of CALR mutant cases of essential thrombocythemia with a cohort of JAK2 V617F-positive essential thrombocythemia (n=57). CALR-positive cases represented 63.7% of double-negative cases of essential thrombocythemia, and most carried CALR type 1 or type 2 indels. However, we also identified one patient who was positive for both the JAK2 V617F and the CALR mutations. This study revealed that CALR mutant essential thrombocythemia is associated with younger age, higher platelet counts, lower erythrocyte counts, leukocyte counts, hemoglobin, and hematocrit, and increased risk of progression to myelofibrosis in comparison with JAK2 V617F-positive essential thrombocythemia. Analysis of the CALR mutant group according to indel type showed that CALR type 1 deletion is strongly associated with male gender. CALR mutant patients had a better overall survival than JAK2 V617F-positive patients, in particular patients of age 60 years or younger. In conclusion, this study in a Belgian cohort of patients supports and extends the growing body of evidence that CALR mutant cases of essential thrombocythemia are phenotypically distinct from JAK2 V617F-positive cases, with regards to clinical and hematologic presentation as well as overall survival.

Presence of calreticulin mutations in JAK2-negative polycythemia vera

Major CALR-mutated clones may be observed in polycythemia vera negative for JAK2 mutations.

Frequency and molecular characteristics of calreticulin gene (CALR) mutations in patients with JAK2 -negative myeloproliferative neoplasms

In 2013, Nangalia et al. and Klampfl et al. found a recurrent and abundant mutation in the calreticulin gene (CALR), mutually exclusive with JAK2 and MPL alterations. At present, the data concerning the new mutation, i.e. its prevalence, allele burden and clinical significance, are scarce. We report the incidence and molecular characteristics of CALR mutations in a group of 184 Polish patients with myeloproliferative neoplasms (MPNs). Clinical data analysis revealed significant differences between JAK2 V617F-mutated and CALR-mutated groups. In essential thrombocythemia patients, hemoglobin levels and leukocyte counts were significantly higher in JAK2-positive than in CALR-positive patients (p = 0.023 and p = 0.017, respectively), but the CALR-positive patients had significantly higher platelet counts (p = 0.022). Patients harboring CALR mutations were also younger at the time of diagnosis (p = 0.039). In primary myelofibrosis patients, the degree of anemia was less severe in those who were CALR exon 9 mutation-positive than in those who were JAK2 V617F-positive (p = 0.048).

Distinct clinical characteristics of myeloproliferative neoplasms with calreticulin mutations

Somatic insertions/deletions in the calreticulin gene have recently been discovered to be causative alterations in myeloproliferative neoplasms. A combination of qualitative and quantitative allele-specific polymerase chain reaction, fragment-sizing, high resolution melting and Sanger-sequencing was applied for the detection of three driver mutations (in Janus kinase 2, calreticulin and myeloproliferative leukemia virus oncogene genes) in 289 cases of essential thrombocythemia and 99 cases of primary myelofibrosis. In essential thrombocythemia, 154 (53%) Janus kinase 2 V617F, 96 (33%) calreticulin, 9 (3%) myeloproliferative leukemia virus oncogene gene mutation-positive and 30 triple-negative (11%) cases were identified, while in primary myelofibrosis 56 (57%) Janus kinase 2 V617F, 25 (25%) calreticulin, 7 (7%) myeloproliferative leukemia virus oncogene gene mutation-positive and 11 (11%) triple-negative cases were identified. Patients positive for the calreticulin mutation were younger and had higher platelet counts compared to Janus kinase 2 mutation-positive counterparts. Calreticulin mutation-positive patients with essential thrombocythemia showed a lower risk of developing venous thrombosis, but no difference in overall survival. Calreticulin mutation-positive patients with primary myelofibrosis had a better overall survival compared to that of the Janus kinase 2 mutation-positive (P=0.04) or triple-negative cases (P=0.01). Type 2 calreticulin mutation occurred more frequently in essential thrombocythemia than in primary myelofibrosis (P=0.049). In essential thrombocythemia, the calreticulin mutational load was higher than the Janus kinase 2 mutational load (P<0.001), and increased gradually in advanced stages. Calreticulin mutational load influenced blood counts even at the time point of diagnosis in essential thrombocythemia. We confirm that calreticulin mutation is associated with distinct clinical characteristics and explored relationships between mutation type, load and clinical outcome.

Calreticulin mutation-specific immunostaining in myeloproliferative neoplasms: pathogenetic insight and diagnostic value

Mutations in the gene calreticulin (CALR) occur in the majority of JAK2- and MPL-unmutated patients with essential thrombocythemia (ET) and primary myelofibrosis (PMF); identifying CALR mutations contributes to the diagnostic pathway of ET and PMF. CALR mutations are heterogeneous spanning over the exon 9, but all result in a novel common protein C terminus. We developed a polyclonal antibody against a 17-amino-acid peptide derived from mutated calreticulin that was used for immunostaining of bone marrow biopsies. We show that this antibody specifically recognized patients harboring different types of CALR mutation with no staining in healthy controls and JAK2- or MPL-mutated ET and PMF. The labeling was mostly localized in megakaryocytes, whereas myeloid and erythroid cells showed faint staining, suggesting a preferential expression of calreticulin in megakaryocytes. Megakaryocytic-restricted expression of calreticulin was also demonstrated using an antibody against wild-type calreticulin and by measuring the levels of calreticulin RNA by gene expression analysis. Immunostaining using an antibody specific for mutated calreticulin may become a rapid, simple and cost-effective method for identifying CALR-mutated patients complementing molecular analysis; furthermore, the labeling pattern supports the preferential expansion of megakaryocytic cell lineage as a result of CALR mutation in an immature hematopoietic stem cell.