Progression in Myeloid Neoplasms: Beyond the Myeloblast.

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

Characteristics, primary treatment, and survival of MDS/MPN with neutrophilia: a population-based study.

Myelodysplastic and myeloproliferative neoplasms (MDS/MPN) with neutrophilia, until recently called atypical chronic myeloid leukemia (aCML), being part of the MDS/MPN is a very rare disease with poor prognosis. Although emerging data reveal its cytogenetic and molecular profile, integrated survival and treatment data remain scarce. We analyzed a cohort of 347 adult patients diagnosed with MDS/MPN with neutrophilia, registered in the Netherlands Cancer Registry between 2001 and 2019. Our demographic baseline data align with other cohorts. We observed cytogenetic aberrations exclusively in patients aged >65 years, with trisomy 8 being the most common abnormality. We identified 16 distinct molecular mutations, with some patients (16/101) harboring up to 3 different mutations; ASXL1 being the most frequent one (22%). In a multivariable Cox regression analysis, only age, hemoglobin level and allogeneic hematopoietic stem cell transplant (alloHSCT) were associated with overall survival (aged >65 years; hazard ratio [HR] 1.85; P = .001 and alloHSCT HR, 0.51; P = .039). Because no other treatment modality seemed to affect survival and might cause toxicity, we propose that all patients eligible for alloHSCT should, whenever possible, receive an allogeneic transplant. It is imperative that we strive to improve outcomes for patients who are not eligible for alloHSCT. Tackling this challenge requires international collaborative efforts to conduct prospective intervention studies.

Haploidentical donor hematopoietic cell transplantation for myelodysplastic/myeloproliferative overlap neoplasms: results from a North American collaboration.

Haploidentical donors offer a potentially readily available donor, especially for non-White patients, for hematopoietic cell transplantation (HCT). In this North American collaboration, we retrospectively analyzed outcomes of first HCT using haploidentical donor and post-transplantation cyclophosphamide (PTCy) in myelodysplastic syndrome/myeloproliferative neoplasm (MDS/MPN) overlap neoplasms (MDS/MPN). We included 120 consecutive patients who underwent HCT using a haploidentical donor for MDS/MPN across 15 centers. Median age was 62.5 years and 38% were of non-White/Caucasian ethnicity. The median follow-up was 2.4 years. Graft failure was reported in seven of 120 (6%) patients. At 3 years, nonrelapse mortality (NRM) was 25% (95% confidence interval [CI]: 17-34), relapse 27% (95% CI: 18-36), grade 3-4 acute graftversus- host disease 12% (95% CI: 6-18), chronic graft-versus-host disease requiring systemic immunosuppression 14% (95% CI: 7-20), progression-free survival (PFS) 48% (95% CI: 39-59), and overall survival (OS) 56% (95% CI: 47-67). On multivariable analysis, NRM was statistically significantly associated with advancing age at HCT (per decade increment, subdistribution hazard ratio [sdHR] =3.28; 95% CI: 1.30-8.25); relapse with the presence of mutation in EZH2/RUNX1/SETBP1 (sdHR=2.61; 95% CI: 1.06-6.44); PFS with advancing age at HCT (per decade increment, HR=1.98, 95% CI: 1.13-3.45); and OS with advancing age at HCT (per decade increment, HR=2.01; 95% CI: 1.11-3.63) and splenomegaly at HCT/prior splenectomy (HR=2.20; 95% CI: 1.04-4.65). Haploidentical donors are a viable option for HCT in MDS/MPN, especially for those disproportionately represented in the unrelated donor registry. Hence, donor mismatch should not preclude HCT for patients with MDS/MPN, an otherwise incurable malignancy. In addition to patient age, disease-related factors including splenomegaly and high-risk mutations dominate outcomes following HCT.

Co-occurring mutations in ASXL1, SRSF2, and SETBP1 define a subset of myelodysplastic/ myeloproliferative neoplasm with neutrophilia.

Identification of genomic signatures with consistent clinicopathological features in myelodysplastic/myeloproliferative neoplasm (MDS/MPN) is critical for improved diagnosis, elucidation of biology, inclusion in clinical trials, and development of therapies. We describe clinical and pathological features with co-existence of mutations in ASXL1 (missense or nonsense), SRSF2, and SKI homologous region of SETBP1, in 18 patients. Median age was 68 years with a male predominance (83%). Leukocytosis and neutrophilia were common at presentation. Marrow features included hypercellularity, granulocytic hyperplasia with megakaryocytic atypia, while the majority had myeloid hyperplasia and/or erythroid hypoplasia, myeloid dysplasia, and aberrant CD7 expression on blasts. Mutations in growth signaling pathways (RAS or JAK2) were noted at diagnosis or acquired during the disease course in 83% of patients. Two patients progressed upon acquisition of FLT3-TKD (acute myeloid leukemia) or KIT (aggressive systemic mastocytosis) mutations. The prognosis is poor with only two long-term survivors, thus far, who underwent blood or marrow transplantation. We propose that the presence of co-occurring ASXL1, SRSF2, and SETBP1 mutations can be diagnostic of a subtype of MDS/MPN with neutrophilia if clinical and morphological findings align. Our report underscores the association between genotype and phenotype within MDS/MPN and that genomic signatures should guide categorization of 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 5th 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.

Clinical characteristics of Japanese patients with myelodysplastic/myeloproliferative neoplasm with ring sideroblasts and thrombocytosis.

Myelodysplastic/myeloproliferative neoplasm with ring sideroblasts and thrombocytosis (MDS/MPN-RS-T) is a rare disease, which presents with features of myelodysplastic syndromes with ring sideroblasts and essential thrombocythemia, as well as anemia and marked thrombocytosis. SF3B1 and JAK2 mutations are often found in patients, and are associated with their specific clinical features. This study was a retrospective analysis of 34 Japanese patients with MDS/MPN-RS-T. Median age at diagnosis was 77 (range, 51-88) years, and patients had anemia (median hemoglobin: 9.0 g/dL) and thrombocytosis (median platelet count: 642 × 109/L). Median overall survival was 70 (95% confidence interval: 68-not applicable) months during the median follow-up period of 26 (range: 0-91) months. A JAK2V617F mutation was detected in 46.2% (n = 12) of analyzed patients (n = 26), while an SF3B1 mutation was detected in 87.5% (n = 7) of analyzed patients (n = 8). Like those with myelodysplastic syndromes or myeloproliferative neoplasms, patients often received erythropoiesis-stimulating agents and aspirin to improve anemia and prevent thrombosis. This study, which was the largest to describe the real-world characteristics of Japanese patients with MDS/MPN-RS-T, showed that the patients had similar characteristics to those in western countries.

Myelodysplastic/myeloproliferative neoplasm with neutrophilia (atypical chronic myeloid leukemia-aCML).

A case of myelodysplastic/myeloproliferative neoplasm with neutrophilia (aCML) with SETBP1 and ASXL1 mutations.

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.

CNL and aCML should be considered as a single entity based on molecular profiles and outcomes.

Chronic neutrophilic leukemia (CNL) and atypical chronic myeloid leukemia (aCML) are rare myeloid disorders that are challenging with regard to diagnosis and clinical management. To study the similarities and differences between these disorders, we undertook a multicenter international study of one of the largest case series (CNL, n = 24; aCML, n = 37 cases, respectively), focusing on the clinical and mutational profiles (n = 53 with molecular data) of these diseases. We found no differences in clinical presentations or outcomes of both entities. As previously described, both CNL and aCML share a complex mutational profile with mutations in genes involved in epigenetic regulation, splicing, and signaling pathways. Apart from CSF3R, only EZH2 and TET2 were differentially mutated between them. The molecular profiles support the notion of CNL and aCML being a continuum of the same disease that may fit best within the myelodysplastic/myeloproliferative neoplasms. We identified 4 high-risk mutated genes, specifically CEBPA (ß = 2.26, hazard ratio [HR] = 9.54, P = .003), EZH2 (ß = 1.12, HR = 3.062, P = .009), NRAS (ß = 1.29, HR = 3.63, P = .048), and U2AF1 (ß = 1.75, HR = 5.74, P = .013) using multivariate analysis. Our findings underscore the relevance of molecular-risk classification in CNL/aCML as well as the importance of CSF3R mutations in these diseases.

Advances in myelodysplastic/myeloproliferative neoplasms.

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

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.

Genetic mutations associated with blood count abnormalities in myeloid neoplasms.

INTRODUCTION: Myelodysplastic syndromes (MDS) predominantly present with varying degrees of cytopenia, while myelodysplastic syndromes/myeloproliferative neoplasms (MDS/MPN) exhibit proliferative features. Genetic defects underlying different complete blood count (CBC) alterations remain to be defined. OBJECTIVE: We aimed to evaluate mutations and impacts on abnormal blood counts in MDS and MDS/MPN. METHOD: MDS and MDS/MPN patients were recruited and sequenced by targeted next-generation sequencing. Clinical parameters, especially CBC, were evaluated for the association with genetic abnormalities and clinical outcomes. RESULTS: A total of 168 patients with myeloid neoplasms were recruited (92 cases of low-risk MDS, 57 cases of high-risk MDS and 19 cases of MDS/MPN). Compared to low-risk MDS and MDS/MPN, patients with high-risk MDS were presented with more severe neutropenia with 17.5% showing absolute neutrophil counts (ANC) lower than 0.5 × 109/L. Patients with MDS/MPN more commonly harboured mutations and had a higher number of mutations per case than low-risk MDS (94.7% vs. 56.5%; p < 0.001 and 3 vs. 1; p < 0.001, respectively). Patients with SF3B1 mutations showed lower haemoglobin levels than wild-type (7.9 vs. 8.4 g/dL, p = 0.02), but were associated with normal platelet counts (286 vs. 93 × 109/L; p < 0.001). Patients with U2AF1 mutations were associated with more severe leukopenia than wild-type (3 vs. 4.18 × 109/L; p = 0.02). KRAS mutations were associated with monocytosis (p < 0.001). Multivariate analysis revealed high-risk MDS, MDS/MPN, severe neutropenia (ANC < 0.5 × 109/L), and mutations in ASXL1 and SETBP1 were associated with inferior survival outcomes. CONCLUSION: Certain mutations were related to more severe anaemia, lower white blood cell count or monocytosis in Asian MDS and MDS/MPN patients.

Clinical and molecular characteristics of acute myeloid leukemia with MPL mutation.

OBJECTIVES: The current study aimed to explore the incidence of MPL mutations and the clinical and molecular characteristics of AML with MPL mutation. METHODS: In total, 1509 patients with newly diagnosed AML were retrospectively analyzed between January 2017 and December 2020. MPL mutations were detected via next-generation sequencing. During the same period, we also enrolled 30 patients with other myeloid neoplasms (MNs) with MPL mutation, which included myelodysplastic syndrome (n = 15), myelodysplastic syndrome/myeloproliferative neoplasm (MDS/MPN) (n = 6), and MPN (n = 9). The clinical characteristics of MPL-mutated AML and other types of MNs or MPL-wide type (MPL-wt) AML were compared, and the spectrum of co-mutations and MPL mutation profiles in MPL-mutated AML were analyzed. RESULTS: MPL mutations were identified in 19 (1.26%) of 1509 patients with AML. The waterfall diagram showed that the co-mutations were mainly epigenetic modifications (TET2, IDH1, and EZH2), spliceosomes (SRSF2), and transcription factors (RUNX1). The platelet count of the AML group was significantly lower than that of the MPN group (p = 0.001). MPL mutations were commonly observed in the intracellular region in AML but the transmembrane region in MPN (p = 0.013). The MPL-mutated AML group had a lower white blood cell count and a lower rate of complete remission than the MPL wild-type AML group (p = 0.037). CONCLUSION: MPL mutations are clinically relevant in patients with AML, and they may be a novel subtype characterized by lower white blood cell counts and poor complete remission rates. However, further studies must be conducted to identify its correlated mechanism.

Panel-based gene testing in myelodysplastic/myeloproliferative neoplasm overlap syndromes: Australasian Leukaemia and Lymphoma Group (ALLG) consensus statement.

This review aims to provide an expert consensus statement to address the role of gene-panel testing in the diagnosis, prognosis and management of adult myelodysplastic syndrome/myeloproliferative neoplasm overlap syndromes (MDS/MPN) in Australia. This consensus statement was developed by an expert group, actively involved in gene panel testing in the area of MDS/MPN in Australia. This work was led by the chairs of the MDS (A/Prof A. Enjeti) and MPN (A/Prof D. Ross) working parties of the Australasian Leukaemia and Lymphoma Group (ALLG). The authors were selected after an expression of interest process on the basis of active laboratory involvement in gene panel testing, a specific demonstrated interest in MDS/MPN and/or publication record in this field. The authors were then allocated sections for literature review to identify the specific genes of interest for each MDS/MPN entity. At least two authors reviewed each section and an overarching diagnostic algorithm was developed by a consensus amongst all authors.

Clinical Application for Diagnosis of Myelodysplatic/Myeloproliferative Neoplasm with Ring Sideroblasts and Thrombocytosis.

BACKGROUND: Myelodysplastic/myeloproliferative neoplasm with ring sideroblasts and thrombocytosis (MDS/ MPN-RS-T) was newly introduced as a full entity in the 2016 revision of the WHO classification. In this study, we investigated the morphologic, laboratory, and clinical features of MDS/MPN-RS-T. METHODS: We reviewed the bone marrow and genetic studies of patients whose diagnoses were coded as "refractory anemia with ring sideroblasts (RARS)" or "MDS/MPN, unclassifiable" between January 2008 and April 2018. RESULTS: A total of 8 cases fulfilled the criteria for a diagnosis of MDS/MPN-RS-T. All of them had no specific symptoms. Half of the cases had less than 450 × 109/L platelet counts by an automated hematology analyzer; however, all platelet counts exceeded 450 × 109/L when performed manually. JAK2 mutation tests were performed in 7 cases, and a heterozygous mutation was detected in 1 case. SF3B1 mutations were present in 3 of the 4 cases tested. CONCLUSIONS: When RARS is suspected in patients without thrombocytopenia, manual platelet counts should be performed. For patients with suspected essential thrombocythemia, RS evaluation through careful observation of an iron-stained slide is crucial. Since the independent evaluation of RS was reflected in the revised classification, the ambiguous disease classification becomes clearer and more consistent.

Genomic landscape of myelodysplastic/myeloproliferative neoplasm can predict response to hypomethylating agent therapy.

There are currently no known predictors of myelodysplastic syndrome (MDS)/myeloproliferative overlap neoplasm (MPN) patients' response to hypomethylating agents (HMA). Forty-three patients with MDS/MPN who were treated with HMA during chronic phase and had next-generation sequencing using the established 63-genes panel were identified. Complete and partial remission and marrow response were assessed based on the MDS/MPN International Working Group response criteria. On univariate analysis, younger age, higher number of mutations, and mutations in SETBP1, RUNX1, or EZH2 were associated with no response. Multivariable analysis for modeling response were conducted via least absolute shrinkage and selection operator logistic regression approach, and showed that mutations in SETBP1, RUNX1, or EZH2 predict lack of HMA response. While limited by sample size, our findings suggest that genomic landscape can potentially identify MDS/MPN patients with lower likelihood of response to HMA.

Myelodysplastic syndrome/myeloproliferative neoplasm with ring sideroblasts and thrombocytosis: Ringing in a new future.

Myelodysplastic syndrome/myeloproliferative neoplasm with ring sideroblasts and thrombocytosis (MDS/MPN-RS-T) is a rare hematologic malignancy belonging to the category of myelodysplastic syndrome (MDS)/myeloproliferative neoplasm (MPN) overlap syndromes. While certain clinical features, including anemia and thrombocytosis, are common to both the MDS and MPN disease components, the biologic consequences of the spliceosome mutation SF3B1 results in notable clinical exceptions. Importantly, both overall and leukemia free survival are shorter for MDS/MPN-RS-T when compared to essential thrombocythemia (ET). In the case of MDS/MPN-RS-T, thrombotic risk is not associated with the presence of JAK2V617F, nor history of prior thrombosis, but is associated with the presence of the mutated spliceosome gene SF3B1. In this review, we highlight the biology, pathology, risk stratification, and treatment approach to MDS/MPN-RS-T. In particular, we focus on clinical management concepts, which are largely borrowed from MDS and MPN, including the use of cytoreduction, bone marrow stimulating agents, and the role of allogeneic stem cell transplantation. We end by highlighting unmet needs and future research priorities in MDS/MPN-RS-T.

Myelodysplastic/myeloproliferative neoplasms with ring sideroblasts and thrombocytosis (MDS/MPN-RS-T): Mayo-Moffitt collaborative study of 158 patients.

The current World Health Organization (WHO) classification of myeloid malignancies includes myelodysplastic/myeloproliferative neoplasms with ring sideroblasts and thrombocytosis (MDS/MPN-RS-T) as a distinct entity. Previous literature on predictors of survival was based on the provisional category of refractory anemia with ring sideroblast and thrombocytosis (RARS-T), which was not subject to MDS/MPN-RS-T exclusionary criteria such as PB blast% ≥1, BM blast% ≥5 or cytogenetic abnormalities such as t(3;3)(q21.2;q26.2), inv(3)(q21.23q26.2) or isolated del(5q). We examined overall (OS) and leukemia-free (LFS) survival and its predictors, among 158 patients with WHO-defined MDS/MPN-RS-T. In univariate analysis, age ≥70 years (P = 0.006), hemoglobin (Hb) ≤10 g/dL (P = 0.03) and abnormal karyotype (excluding -Y, P = 0.008) were associated with shortened OS, which was otherwise not affected by either ASXL1 (P = 0.7), SF3B1 (P = 0.4) or JAK2 V617F (P = 0.7) mutations; in multivariable analysis, Hb ≤ 10 g/dL (P = 0.03) and abnormal karyotype (P = 0.001) remained significant, and thus allowed the development of an operational survival model with low (0 risk factors, median OS 10.5 years), intermediate (1 risk factor, median OS 4.8 years) and high risk (2 risk factors, median OS 1.4 years) categories (P = 0.0009). Comparison of MDS/MPN-RS-T (n = 158) and MDS/MPN-U with BM RS ≥ 15% (MDS/MPN-U-RS; n = 25) did not reveal significant differences in frequency of thrombosis, OS, or LFS, although SF3B1 mutation frequency was higher in the former (93% versus 59%; P = 0.0005). These data suggest limited survival impact for molecular abnormalities and the morphological distinction between MDS/MPN-RS-T and MDS/MPN-U-RS.