Predictors of clinical outcome in myeloproliferative neoplasm, unclassifiable: A Bone Marrow Pathology Group study.

OBJECTIVES: Myeloproliferative neoplasm, unclassifiable (MPN-U, revised to MPN, not otherwise specified in the fifth edition of the World Health Organization classification) is a heterogeneous category of primary marrow disorders with clinical, morphologic, and/or molecular features that preclude classification as a more specific MPN subtype due to stage at diagnosis, overlapping features between MPN subtypes, or the presence of coexisting disorders. Compared with other MPN subtypes, the contribution of the mutational landscape in MPN-U in conjunction with other clinical and morphologic biomarkers to prognosis has been less well investigated. METHODS: We performed a multicenter, retrospective study of MPN-U (94 cases) to better define the clinicopathologic features, genetic landscape, and clinical outcomes, including subgroups of early-stage, advanced-stage, and coexisting disorders. The Dynamic International Prognostic Scoring System (DIPSS) plus scoring system was applied to assess its relevance to MPN-U prognosis. RESULTS: Multivariate analysis demonstrated bone marrow blast count and DIPSS plus score as statistically significant in predicting overall survival. Univariate analysis identified additional potential poor prognostic markers, including abnormal karyotype and absence of JAK2 mutation. Secondary mutations were frequent in the subset analyzed by next-generation sequencing (26/37 cases, 70.3%) with a borderline association between high molecular risk mutations and overall survival. CONCLUSIONS: This study, as one of the largest of MPN-U studies incorporating both clinicopathologic and molecular data, moves toward identification of biomarkers that better predict prognosis in this heterogeneous category.

Prognostic impact of SF3B1 mutation and multilineage dysplasia in myelodysplastic syndromes with ring sideroblasts: a Mayo Clinic study of 170 informative cases.

The revised 4th edition of the World Health Organization (WHO4R) classification lists myelodysplastic syndromes with ring sideroblasts (MDS-RS) as a separate entity with single lineage (MDS-RS-SLD) or multilineage (MDS-RS-MLD) dysplasia. The more recent International Consensus Classification (ICC) distinguishes between MDS with SF3B1 mutation (MDS-SF3B1) and MDS-RS without SF3B1 mutation; the latter is instead included under the category of MDS not otherwise specified. The current study includes 170 Mayo Clinic patients with WHO4R-defined MDS-RS, including MDS-RS-SLD (N=83) and MDS-RS-MLD (N=87); a subset of 145 patients were also evaluable for the presence of SF3B1 and other mutations, including 126 with (87%) and 19 (13%) without SF3B1 mutation. Median overall survival for all 170 patients was 6.6 years with 5- and 10-year survival rates of 59% and 25%, respectively. A significant difference in overall survival was apparent between MDS-RS-MLD and MDS-RS-SLD (p<0.01) but not between MDS-RS with and without SF3B1 mutation (p=0.36). Multivariable analysis confirmed the independent prognostic contribution of MLD (HR 1.8, 95% CI 1.1-2.8; p=0.01) and also identified age (p<0.01), transfusion need at diagnosis (p<0.01), and abnormal karyotype (p<0.01), as additional risk factors; the impact from SF3B1 or other mutations was not significant. Leukemia-free survival was independently affected by abnormal karyotype (p<0.01), RUNX1 (0.02) and IDH1 (p=0.01) mutations, but not by MLD or SF3B1 mutation. Exclusion of patients not meeting ICC-criteria for MDSSF3B1 did not change the observations on overall survival. MLD-based, as opposed to SF3B1 mutationbased, disease classification for MDS-RS might be prognostically more relevant.

TP53 variant allele frequency and therapy-related setting independently predict survival in myelodysplastic syndromes with del(5q).

Among 210 patients with myelodysplastic syndromes (MDSs) with del(5q), molecular information was available at diagnosis or at least 3 months before leukaemic transformation in 146 cases. Multivariate analysis identified therapy-related setting (p = 0.02; HR 2.3) and TP53 variant allele frequency (VAF) ≥22% (p < 0.01; HR 2.8), but not SF3B1 mutation (p = 0.65), as independent risk factors for survival. Median survival was 11.7 versus 4 years (5/10-year survival 73%/52% vs. 42%/14%) in the absence (N = 112) versus presence (N = 34) of ≥1 risk factors; leukaemia-free survival was affected by TP53 VAF ≥22% (p < 0.01). Such information might inform treatment decision-making in MDS-del(5q) regarding allogeneic stem cell transplant.

Acute Lymphoblastic Leukemia with Myeloid Mutations Is a High-Risk Disease Associated with Clonal Hematopoiesis.

Myeloid neoplasms arise from preexisting clonal hematopoiesis (CH); however, the role of CH in the pathogenesis of acute lymphoblastic leukemia (ALL) is unknown. We found that 18% of adult ALL cases harbored TP53, and 16% had myeloid CH-associated gene mutations. ALL with myeloid mutations (MyM) had distinct genetic and clinical characteristics, associated with inferior survival. By using single-cell proteogenomic analysis, we demonstrated that myeloid mutations were present years before the diagnosis of ALL, and a subset of these clones expanded over time to manifest as dominant clones in ALL. Single-cell RNA sequencing revealed upregulation of genes associated with cell survival and resistance to apoptosis in B-ALL with MyM, which responds better to newer immunotherapeutic approaches. These findings define ALL with MyM as a high-risk disease that can arise from antecedent CH and offer new mechanistic insights to develop better therapeutic and preventative strategies. SIGNIFICANCE: CH is a precursor lesion for lymphoblastic leukemogenesis. ALL with MyM has distinct genetic and clinical characteristics, associated with adverse survival outcomes after chemotherapy. CH can precede ALL years before diagnosis, and ALL with MyM is enriched with activated T cells that respond to immunotherapies such as blinatumomab. See related commentary by Iacobucci, p. 142.

STAT5B mutations in myeloid neoplasms differ by disease subtypes but characterize a subset of chronic myeloid neoplasms with eosinophilia and/or basophilia.

STAT5B has been reported as a recurrent mutation in myeloid neoplasms (MNs) with eosinophilia, but the overall frequency and importance across a spectrum of MNs are largely unknown. We conducted a multicenter study on a series of 82 MNs with STAT5B mutations detected by next-generation sequencing. The estimated frequency of STAT5B mutation in MNs was low.

Presence but not number of secondary type mutations influences outcome in de novo AML without MDS-associated or recurring cytogenetic abnormalities.

A group of gene mutations has been identified to be strongly associated with secondary acute myeloid leukemias (AML) arising from prior myeloid neoplasms. The International Consensus Classification (ICC) and proposed 5th edition of the World Health Organization (WHO) classification differ by inclusion of RUNX1. A recent study suggested that having two or more secondary mutations is associated with a particularly poor prognosis. In a study of 294 de novo AML patients, we found that patients with at least one ICC-defined secondary mutation had shorter survival when compared to those without secondary mutations, and ICC/WHO groups of two or more mutations did not predict for worse outcomes.

The international consensus classification of eosinophilic disorders and systemic mastocytosis.

Based on new data and increased understanding of disease molecular genetics, the international consensus classification (ICC) has made several changes in the diagnosis and classification of eosinophilic disorders and systemic mastocytosis. Myeloid/lymphoid neoplasms with eosinophilia (M/LN-eo) and gene rearrangements have been renamed as M/LN-eo with tyrosine kinase gene fusions (M/LN-eo-TK). The category has been expanded to include ETV6::ABL1 and FLT3 fusions, and to accept PCM1::JAK2 and its genetic variants as formal members. The overlaps and differences between M/LN-eo-TK and BCR::ABL1-like B-lymphoblastic leukemia (ALL)/de novo T-ALL sharing the same genetic lesions are addressed. Besides genetics, ICC for the first time has introduced bone marrow morphologic criteria in distinguishing idiopathic hypereosinophilia/hypereosinophilic syndrome from chronic eosinophilic leukemia, not otherwise specified. The major diagnostic criteria for systemic mastocytosis (SM) in the ICC remain largely based on morphology, but several minor modifications/refinements have been made in criteria related to diagnosis, subclassification, and assessment of disease burden (B- and C-findings). This review is to focus on the ICC updates related to these disease entities, illustrated through changes related to morphology, molecular genetics, clinical features, prognosis, and treatment. Two practical algorithms are provided in navigating through the diagnosis and classification systems of hypereosinophilia and SM.

Guide to the Diagnosis of Myeloid Neoplasms: A Bone Marrow Pathology Group Approach.

OBJECTIVES: The practicing pathologist is challenged by the ever-increasing diagnostic complexity of myeloid neoplasms. This guide is intended to provide a general roadmap from initial case detection, often triggered by complete blood count results with subsequent blood smear review, to final diagnosis. METHODS: The integration of hematologic, morphologic, immunophenotypic, and genetic features into routine practice is standard of care. The requirement for molecular genetic testing has increased along with the complexity of test types, the utility of different testing modalities in identifying key gene mutations, and the sensitivity and turnaround time for various assays. RESULTS: Classification systems for myeloid neoplasms have evolved to achieve the goal of providing a pathology diagnosis that enhances patient care, outcome prediction, and treatment options for individual patients and is formulated, endorsed, and adopted by hematologists/oncologists. CONCLUSIONS: This guide provides diagnostic strategies for all myeloid neoplasm subtypes. Special considerations are provided for each category of testing and neoplasm category, along with classification information, genetic testing requirements, interpretation information, and case reporting recommendations based on the experience of 11 Bone Marrow Pathology Group members.

Acute leukemias with complex karyotype show a similarly poor outcome independent of mixed, myeloid or lymphoblastic immunophenotype: A study from the Bone Marrow Pathology Group.

Mixed phenotype acute leukemia (MPAL) is a heterogenous group of acute leukemias characterized by leukemic blasts that express markers of multiple lineages. The revised 4th edition WHO classification of MPAL excludes AML with myelodysplasia related changes (AML-MRC), including those with complex karyotype (CK), from a diagnosis of MPAL. Abnormal karyotype is frequent in MPAL with the reported rate of CK in MPAL ranging from 19% to 32%. Due its rarity, the clinical and genetic features of MPAL with CK remain poorly characterized. This study aims to further characterize the genetic features of MPAL with CK in comparison to cases of AML and ALL with CK. Cases of de novo MPAL, AML, and B- and T-ALL patients with CK were collected from 8 member institutions of the Bone Marrow Pathology Group. We found no significant difference in overall survival between MPAL with CK compared to AML and ALL with CK. AML with CK was more strongly associated with TP53 mutations, however the presence of TP53 mutations conferred a worse prognosis regardless of lineage. ALL with CK seems to show increased IKZF1 mutation rates which is known to confer a worse prognosis in ALL. Additionally, MPAL with CK showed similarly poor outcomes regardless of whether a lymphoid or myeloid chemotherapy regimen is chosen. Our results suggest that acute leukemias with complex karyotype show a similarly poor outcome regardless of lineage differentiation and that mutation in TP53 confers a poor prognosis in all lineages. Our results support the exclusion of immunophenotypic MPAL with CK from MPAL and appear to confirm the approach proposed in the revised 4th edition WHO to include them as AML with myelodysplasia-related changes and similar myelodysplasia-related AML categories of newer classifications.

Myeloid sarcoma with NPM1 mutation may be clinically and genetically distinct from AML with NPM1 mutation: a study from the Bone Marrow Pathology Group.

Myeloid sarcoma (MS) is currently considered equivalent to de novo acute myeloid leukemia (AML); however, the relationship between these entities is poorly understood. This retrospective multi-institutional cohort study compared 43 MS with NPM1 mutation to 106 AML with NPM1 mutation. Compared to AML, MS had more frequent cytogenetic abnormalities including complex karyotype (p = .009 and p = .007, respectively) and was enriched in mutations of genes involved in histone modification, including ASXL1 (p = .007 and p = .008, respectively). AML harbored a higher average number of gene mutations (p = .002) including more frequent PTPN11 mutations (p < .001) and mutations of DNA-methylating genes including DNMT3A and IDH1 (both p < .001). MS had significantly shorter overall survival (OS) than AML (median OS: 44.9 vs. 93.2 months, respectively, p = .037). MS with NPM1 mutation has a unique genetic landscape, and poorer OS, compared to AML with NPM1 mutation.

First study comparing genetic profiles of MS and AML with a common disease-defining lesion.NPM1^Mut MS may be genetically distinct from NPM1^Mut AML.NPM1^Mut MS may have inferior overall survival compared to NPM1^Mut AML.

Triple-Negative Primary Myelofibrosis: A Bone Marrow Pathology Group Study.

Primary myelofibrosis (PMF) is a clonal myeloproliferative neoplasm driven by canonical gene mutations in JAK2, CALR, or MPL in >80% of the cases. PMF that lacks these canonical alterations is termed triple-negative PMF (TN-PMF). The pathologic and genetic characteristics of TN-PMF compared with those of conventional PMF with canonical driver mutations (DM-PMF) have not been well studied. We aimed to identify clinicopathologic and molecular genetic differences between patients with TN-PMF (n = 56) and DM-PMF (n = 89), all of whom fulfilled the 2016 World Health Organization diagnostic criteria for PMF. Compared with the control group, patients in the TN-PMF group were more likely to have thrombocytopenia and less likely to have organomegaly. The bone marrow in patients with TN-PMF showed fewer granulocytic elements and more frequent dyserythropoiesis. Cytogenetic analysis showed a higher incidence of trisomy 8. Targeted next-generation sequencing revealed a lower frequency of ASXL1 mutations but enrichment of ASXL1/SRSF2 comutations. Our findings demonstrated several clinicopathologic and molecular differences between TN-PMF and DM-PMF. These findings, particularly the observed mutation profile characterized by a higher frequency of ASXL1 and SRSF2 comutation, suggest that at least a subset of TN-PMF may be pathogenetically different from DM-PMF, with potential prognostic implications.

Clinicopathologic characteristics of myeloproliferative neoplasms with JAK2 exon 12 mutation.

The presence of JAK2 exon 12 mutation was included by the 2016 World Health Organization (WHO) Classification as one of the major criteria for diagnosing polycythemia vera (PV). Few studies have evaluated the clinical presentation and bone marrow morphology of these patients and it is unclear if these patients fulfill the newly published criteria of 5th edition WHO or The International Consensus Classification (ICC) criteria for PV. Forty-three patients with JAK2 exon 12 mutations were identified from the files of 7 large academic institutions. Twenty patients had complete CBC and BM data at disease onset. Fourteen patients met the diagnostic criteria for PV and the remaining six patients were diagnosed as MPN-U. At diagnosis, 9/14 patients had normal WBC and platelet counts (isolated erythrocytosis/IE subset); while 5/14 had elevated WBC and/or platelets (polycythemic /P subset). We found that hemoglobin and hematocrit tended to be lower in the polycythemia group. Regardless of presentation (P vs IE), JAK2 deletion commonly occurred in amino acids 541-544 (62 %). MPN-U patients carried JAK2 exon 12 mutation, but did not fulfill the criteria for PV. Half of the patients had hemoglobin/hematocrit below the diagnostic threshold for PV, but showed increased red blood cell count with low mean corpuscular volume (56-60 fL). Three cases lacked evidence of bone marrow hypercellularity. In summary, the future diagnostic criteria for PV may require a modification to account for the variant CBC and BM findings in some patients with JAK2 exon 12 mutation.

Clinicopathologic and Molecular Analysis of Normal Karyotype Therapy-Related and De Novo Acute Myeloid Leukemia: A Multi-Institutional Study by the Bone Marrow Pathology Group.

PURPOSE: Therapy-related acute myeloid leukemias (t-AML) are a heterogenous group of aggressive neoplasms that arise following exposure to cytotoxic chemotherapy and/or ionizing radiation. Many therapy-related myeloid neoplasms (t-MN) are associated with distinct chromosomal aberrations and/or TP53 alterations, but little is known about the clinicopathologic and molecular features of normal karyotype t-AML (NK-t-AML) and whether this t-MN subtype is distinctly different from NK de novo AML (NK-dn-AML). METHODS: This multi-institutional study by the Bone Marrow Pathology Group retrospectively evaluated clinicopathologic and molecular characteristics of 335 patients with NK-AML, comprising 105 t-AML and 230 dn-AML cases. RESULTS: Patients with t-AML compared with dn-AML exhibit significantly shorter overall survival (OS; median months: 17.6 v 44.2; P < .0001) and relapse-free survival (RFS; median months: 9.1 v 19.2; P = .0018). Frequency of NPM1, FLT3, KRAS, and GATA2 mutations were significantly different in NK-t-AML compared with NK-dn-AML (NPM1 35% v 49%; P = .0493; FLT3 23% v 36%; P = 0494; KRAS 12% v 5%; P = .0465; GATA2 9% v 2% P = .0105), while TP53 mutations were rare. Patients with t-AML more often stratified into intermediate or adverse 2017 ELN genetic risk groups. Favorable ELN risk predicted favorable OS (hazard ratio [HR], 0.4056; 95% CI, 0 to 0.866; P = .020) and RFS (HR, 0.355; 95% CI, 0 to 0.746; P = .006). Among all patients with NK-AML, stem-cell transplant and favorable ELN risk both significantly affected RFS, while therapy-relatedness and age had a borderline significant impact on OS (HR, 1.355; 95% CI, 0.975 to 1.882; P = .070). CONCLUSION: To our knowledge, this is the largest study to date to comprehensively evaluate NK-t-AML and provides a framework that may inform our understanding of NK-t-AML disease biology and could potentially help guide therapeutic management and improved disease classification in t-MNs that lack cytogenetic aberrations.

The international consensus classification of myeloid neoplasms and acute Leukemias: myeloproliferative neoplasms.

A group of international experts, including hematopathologists, oncologists, and geneticists were recently summoned (September 2021, Chicago, IL, USA) to update the 2016/17 World Health Organization classification system for hematopoietic tumors. After careful deliberation, the group introduced the new International Consensus Classification (ICC) for Myeloid Neoplasms and Acute Leukemias. This current in-depth review focuses on the ICC-2022 category of JAK2 mutation-prevalent myeloproliferative neoplasms (MPNs): essential thrombocythemia, polycythemia vera, primary myelofibrosis, and MPN, unclassifiable. The ICC MPN subcommittee chose to preserve the primary role of bone marrow morphology in disease classification and diagnostics, while also acknowledging the complementary role of genetic markers for establishing clonality, facilitating MPN subtype designation, and disease prognostication.

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.