Autoimmune myelofibrosis: A Mayo Clinic series of 22 patients

We describe the clinical phenotype, management strategies and outcomes of 22 patients with autoimmune myelofibrosis (AIMF); median age: 45 years; 77% females; 83% with autoimmune disease, pancytopenia in 32% and transfusion-requiring anaemia in 59%. All informative cases were negative for JAK2 (n = 18) and CALR/MPL mutations (n = 12). Fourteen of nineteen (74%) evaluable patients achieved complete response (CR) based on the resolution of cytopenias. First-line treatments included steroids +/- immunosuppressive agents, cyclosporin and mycophenolate with CR in 7 of 13 (54%), 1 of 2 (50%) and 1 of 2 (50%) respectively. Rituximab salvage therapy yielded CR in 4 of 5 (80%) cases. The current study provides information on steroid-sparing treatments for AIMF.

Incidental discovery of KIT-mutated mastocytoma in a colon polyp

Mastocytoma in a colon polyp positive for tryptase, CD117/KIT, S100, weakly positive for CD25.

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

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

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.

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.

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.

Reappraisal of mast cell leukemia based on a single institution review of 16 cases: Mast cell morphology determines clinical outcome

Cytologic abnormalities of atypical mast cells in mastocytosis. The mature mast cells have oval-shaped nuclei, cytoplasmic hypogranulation and spindle-shaped cytology. or well-differentiated displaying a round nucleus with condensed chromatin, and abundant dense cytoplasmic granulations. Immature mast cells include promastocytes and metachromatic blast-like forms.

Granularity in disease classification impacts survival prediction in advanced systemic mastocytosis: A single institution study of 329 informative cases

The World Health Organization (WHO) classification system categorizes advanced systemic mastocytosis (SM-Adv) into aggressive SM (ASM), mast cell leukemia (MCL), and SM with associated hematological neoplasm (SM-AHN). By contrast, the International Consensus Classification (ICC) requires "immature" MC cytomorphology for the diagnosis of MCL and limits SM-AHN to myeloid neoplasms (SM-AMN). The current study includes 329 patients with SM-Adv (median age 65 years, range 18-88; males 58%): WHO subcategories SM-AHN (N = 212; 64%), ASM (N = 99; 30%), and MCL (N = 18; 6%); ICC subcategories SM-AMN (N = 190; 64%), ASM (N = 99; 33%), and MCL (N = 9; 3%); WHO-defined MCL with "mature" MC cytomorphology and SM-AHN associated with lymphoid neoplasms were operationally labeled as "MCL-mature" (N = 9) and SM-ALN (N = 22), respectively, and distinguished from ICC-defined MCL and SM-AMN. Multivariable analysis that included the Mayo alliance risk factors for survival in SM (age >60 years, anemia, thrombocytopenia, increased alkaline phosphatase) revealed more accurate survival prediction with the ICC versus WHO classification order: (i) survival was significantly worse with MCL-immature versus MCL-mature (hazard ratio [HR] 15; p < .01), (ii) prognostic distinction between MCL and SM-AHN/AMN was confirmed in the context of ICC (HR 9.3; p < .01) but not WHO classification order (p = .99), (iii) survival was similar between MCL-mature and SM-AMN (p = .18), and (iv) SM-AMN (HR 1.7; p < .01) but not SM-ALN (p = .37) was prognostically distinct from ASM. The current study provides evidence for the independent prognostic contribution of both the ICC system for SM-Adv and the Mayo alliance risk factors for survival in SM.

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.

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.

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.

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.

What’s New in the Classification, Diagnosis and Therapy of Myeloid Leukemias

Myeloid leukemias are a broad group of hematological disorders, characterized by heterogeneous clinical and biological features. In recent years, unprecedented genetic discoveries and clinical–biological correlations have revolutionized the field of myeloid leukemias. The most relevant changes have specifically occurred in acute myeloid leukemia (AML), chronic myelomonocytic leukemia (CMML), chronic myeloid leukemia (CML) and myeloid neoplasms (MNs) with eosinophilia. The recently published International Consensus Classification (ICC) of myeloid neoplasms has addressed these changes, providing an updated framework and revised diagnostic criteria for such entities. This is also the aim of the 5th edition of the WHO classification of hematopoietic tumors, whose preliminary version was published in 2022. Parallel to this, new therapeutic options and novel molecular targets have changed the management of many myeloid entities, including AML and CML. This review aims to address the most relevant updates in the classification and diagnosis of AML, CMML, CML and MNs with eosinophilia. The state of the art of treatment and future therapeutic options for such disorders are also discussed.

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.

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 mastocytosis and related entities

Mastocytosis is a neoplasm characterized by a clonal proliferation of mast cells, which accumulate in one or multiple organs, associated with an extremely heterogeneous clinical presentation. The disease can be limited to the skin (cutaneous mastocytosis) that is mostly seen in childhood and usually behaves in a benign fashion. Adult patients most often present with systemic disease with or without skin lesions. This includes indolent forms such as indolent systemic mastocytosis and its subvariant bone marrow mastocytosis, and smoldering systemic mastocytosis as well as aggressive forms including aggressive systemic mastocytosis, systemic mastocytosis with an associated myeloid neoplasm (previously called systemic mastocytosis with an associated hematologic neoplasm), and mast cell leukemia. In addition, mast cell sarcoma is a rare aggressive form of mastocytosis that can present in the skin as well as at extracutaneous sites. This review article focuses on the updates in mastocytosis of the 2022 international consensus classification (ICC).

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.

The International Consensus Classification of myelodysplastic syndromes and related entities

The International Consensus Classification (ICC) of myeloid neoplasms and acute leukemia has updated the classification of myelodysplastic syndromes (MDSs) and placed MDS in a broader group of clonal cytopenias that includes clonal cytopenia of undetermined significance (CCUS) and related entities. Although subject to some interobserver variability and lack of specificity, morphologic dysplasia remains the main feature that distinguishes MDS from other clonal cytopenias and defines MDS as a hematologic malignancy. The ICC has introduced some changes in the definition of MDS whereby some cases categorized as MDS based on cytogenetic abnormalities are now classified as CCUS, while SF3B1 and multi-hit TP53 mutations are now considered to be MDS-defining in a cytopenic patient. The ICC has also recognized several cytogenetic and molecular abnormalities that reclassify some cases of MDS with excess blasts as acute myeloid leukemia (AML) and has introduced a new MDS/AML entity that encompasses cases with 10-19% blasts that lie on the continuum between MDS and AML. Two new genetically defined categories of MDS have been introduced: MDS with mutated SF3B1 and MDS with mutated TP53, the latter requiring bi-allelic aberrations in the TP53 gene. The entity MDS, unclassifiable has been eliminated. These changes have resulted in an overall simplification of the MDS classification scheme from 8 separate entities (including 1 that was genetically defined) in the revised 4th edition WHO classification to 7 separate entities (including 3 that are genetically defined) in the ICC.

Updates on eosinophilic disorders

This review addresses changes and updates in eosinophilic disorders under the International Consensus Classification (ICC). The previous category of myeloid/lymphoid neoplasm with eosinophilia (M/LN-eo) and a specific gene rearrangement is changed to M/LN-eo with tyrosine kinase gene fusions to reflect the underlying genetic lesions. Two new members, M/LN-eo with ETV6::ABL1 fusion and M/LN-eo with various FLT3 fusions, have been added to the category; and M/LN-eo with PCM1::JAK2 and its genetic variants ETV6::JAK2 and BCR::JAK2 are recognized as a formal entity from their former provisional status. The updated understanding of the clinical and molecular genetic features of PDGFRA, PDGFRB and FGFR1 neoplasms is summarized. Clear guidance as to how to distinguish these fusion gene-associated disorders from the overlapping entities of Ph-like B-acute lymphoblastic leukemia (ALL), de novo T-ALL, and systemic mastocytosis is provided. Bone marrow morphology now constitutes one of the diagnostic criteria of chronic eosinophilic leukemia, NOS (CEL, NOS), and idiopathic hypereosinophilia/hypereosinophilic syndrome (HE/HES), facilitating the separation of a true myeloid neoplasm with characteristic eosinophilic proliferation from those of unknown etiology and not attributable to a myeloid neoplasm.

International Consensus Classification of myeloid and lymphoid neoplasms: myeloproliferative neoplasms

The recently published International Consensus Classification (ICC) of myeloid neoplasms summarized the results of an in-depth effort by pathologists, oncologists, and geneticists aimed to update the 2017 World Health Organization classification system for hematopoietic tumors. Along these lines, several important modifications were implemented in the classification of myeloproliferative neoplasms (MPNs). For chronic myeloid leukemia, BCR::ABL1-positive, the definition of accelerated and blast phase was simplified, and in the BCR::ABL1-negative MPNs, the classification was slightly updated to improve diagnostic specificity with a more detailed and better validated morphologic approach and the recommendation of more sensitive molecular techniques to capture in particular early stage diseases. In this regard, high sensitive single target (RT-qPCR, ddPCR) or multi-target next-generation sequencing assays with a minimal sensitivity of VAF 1% are now important for a proper diagnostic identification of MPN cases with low allelic frequencies at initial presentation. This review discusses the updated diagnostic criteria of MPN according to the ICC, particularly by highlighting the new concepts and how they can be applied in clinical settings to obtain an appropriate prognostic relevant diagnosis.

The International Consensus Classification of acute myeloid leukemia

Acute myeloid leukemias (AMLs) are overlapping hematological neoplasms associated with rapid onset, progressive, and frequently chemo-resistant disease. At diagnosis, classification and risk stratification are critical for treatment decisions. A group with expertise in the clinical, pathologic, and genetic aspects of these disorders developed the International Consensus Classification (ICC) of acute leukemias. One of the major changes includes elimination of AML with myelodysplasia-related changes group, while creating new categories of AML with myelodysplasia-related cytogenetic abnormalities, AML with myelodysplasia-related gene mutations, and AML with mutated TP53. Most of recurrent genetic abnormalities, including mutations in NPM1, that define specific subtypes of AML have a lower requirement of ≥ 10% blasts in the bone marrow or blood, and a new category of MDS/AML is created for other case types with 10-19% blasts. Prior therapy, antecedent myeloid neoplasms or underlying germline genetic disorders predisposing to the development of AML are now recommended as qualifiers to the initial diagnosis of AML. With these changes, classification of AML is updated to include evolving genetic, clinical, and morphologic findings.

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.

Genomic profiling for clinical decision making in myeloid neoplasms and acute leukemia

Myeloid neoplasms and acute leukemias derive from the clonal expansion of hematopoietic cells driven by somatic gene mutations. Although assessment of morphology plays a crucial role in the diagnostic evaluation of patients with these malignancies, genomic characterization has become increasingly important for accurate diagnosis, risk assessment, and therapeutic decision making. Conventional cytogenetics, a comprehensive and unbiased method for assessing chromosomal abnormalities, has been the mainstay of genomic testing over the past several decades and remains relevant today. However, more recent advances in sequencing technology have increased our ability to detect somatic mutations through the use of targeted gene panels, whole-exome sequencing, whole-genome sequencing, and whole-transcriptome sequencing or RNA sequencing. In patients with myeloid neoplasms, whole-genome sequencing represents a potential replacement for both conventional cytogenetic and sequencing approaches, providing rapid and accurate comprehensive genomic profiling. DNA sequencing methods are used not only for detecting somatically acquired gene mutations but also for identifying germline gene mutations associated with inherited predisposition to hematologic neoplasms. The 2022 International Consensus Classification of myeloid neoplasms and acute leukemias makes extensive use of genomic data. The aim of this report is to help physicians and laboratorians implement genomic testing for diagnosis, risk stratification, and clinical decision making and illustrates the potential of genomic profiling for enabling personalized medicine in patients with hematologic neoplasms.

Pure (acute) erythroid leukemia: morphology, immunophenotype, cytogenetics, mutations, treatment details, and survival data among 41 Mayo Clinic cases

Pure erythroid leukemia (PEL), also known as acute erythroid leukemia (AEL), is recognized as a distinct morphologic entity by both the 2016 and 2022 World Health Organization (WHO) classification system. By contrast, the 2022 International Consensus Classification (ICC) includes PEL under a broader category of "acute myeloid leukemia with mutated TP53". We identified 41 Mayo Clinic cases of PEL (mean age 66 years, range 27-86; 71% males) and provide a comprehensive account of bone marrow morphology, immunophenotype, cytogenetic and mutation profiles. PEL was primary in 14 cases, therapy-related in 14, secondary in 12, and undetermined in one. All cases expressed biallelic TP53 alterations, including TP53 deletion/single TP53 mutation (68%), two TP53 mutations (29%) or two TP53 deletions (3%); additional mutations were infrequent. Karyotype was complex in all cases and monosomal in 90%. Treatment details were available in 29 patients: hypomethylating agent (HMA) alone (n = 5), HMA + venetoclax (n = 12), intensive chemotherapy (n = 4), supportive care/other (n = 8); no responses or allogeneic stem cell transplants were documented, and all patients died at a median 1.8 months (range 0.2-9.3). The current study highlights a consistent and reproducible set of morphologic and genetic characteristics that identify PEL as a distinct AML variant whose dismal prognosis requires urgent attention.

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

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

Of drills and bones: Giovanni Ghedini and the origin of bone marrow biopsy

Bone marrow (BM) studies are pivotal for the diagnosis of haematological disorders. Their introduction into clinical haematology dates back to the work of Giovanni Ghedini (1877-1959), an Italian physician who first conceived BM sampling in 1908. Ghedini's proposal stemmed from his clinical experience and from the scientific developments that characterised his epoch. By presenting selected passages of Ghedini's publications, this report considers the theoretical and historical bases of his work and analyses its practical implications for modern haematology.

How I Diagnose Primary Myelofibrosis

OBJECTIVES

Primary myelofibrosis (PMF) is a BCR/ABL1-negative myeloproliferative neoplasm (MPN) with a shorter overall survival and a higher leukemic transformation than other BCR/ABL1-negative MPNs. Diagnosis of PMF can be challenging given its clinical, morphologic, molecular overlap with other myeloid neoplasms also associated with myelofibrosis, and reactive conditions.

METHODS

We summarize and discuss the clinical, morphologic, and molecular features useful for diagnosing PMF as well as salient features helpful in distinguishing PMF from myelodysplastic syndrome with associated fibrosis and autoimmune myelofibrosis using a case-based approach.

RESULTS

PMF in both its prefibrotic and fibrotic stages, the latter characterized by reticulin/collagen marrow fibrosis, is characterized by a proliferation of predominantly abnormal megakaryocytes and granulocytes in the bone marrow. Driver mutations in   JAK2, CALR, or MPLare seen in approximately 90% of PMF cases. In triple-negative cases, the presence of cytogenetic abnormalities and other somatic mutations identified by next-generation sequencing can help establish a diagnosis of PMF in the appropriate clinical and morphologic context.

CONCLUSIONS

Given the significant difference in prognosis and treatment, integration of clinical, morphological, and molecular/genetic findings is essential in distinguishing PMF from other etiologies that can demonstrate myelofibrosis.

Myeloid/lymphoid neoplasms with FLT3 rearrangement

Myeloid/lymphoid neoplasms (M/LN) with 13q12/FLT3 rearrangement have been suggested as candidates for possible inclusion in the World Health Organization classification group of M/LN with eosinophilia (M/LN-eo). We report 12 patients with confirmed FLT3 rearrangement, six with t(12;13)/ETV6-FLT3; one with ins(13;22)/BCR-FLT3; and five with an unconfirmed partner gene located on chromosome bands 2p16, 3q27, 5q15, 5q35, and 7q36. Disease presentations were heterogeneous, including lymphoblastic leukemia/lymphoma, myeloid sarcoma, chronic eosinophilic leukemia, chronic myelomonocytic leukemia, and myelodysplastic syndrome. However, some common features were observed, such as extramedullary involvement (n = 7, 58%), associated eosinophilia in blood, bone marrow, or tissue (n = 8, 67%), multilineage involvement, either as biphasic myeloid/lymphoid neoplasms (n = 2) or mixed phenotype acute leukemia (n = 2). Mutations were detected in 4/8 (50%) patients by next-generation sequencing. None (0/10) had FLT3 or KIT mutations. Eleven patients received disease-based chemotherapy or hypomethylating agents, three received FLT3 inhibitors, and five patients proceeded to hematopoietic stem cell transplant. Together with a review of 16 cases published in the literature, it is apparent that M/LNs with FLT3 rearrangement show disease features reminiscent of members in the category of M/LN-eo with PDGFRA, PDGFRB, FGFR1, and PCM1/JAK2 rearrangement, characterized by a specific gene rearrangement, frequent eosinophilia, multi-lineage involvement and therapeutic benefit from kinase inhibitors.

Discordant PET Findings and a High Relapse Rate Characterize Hispanics With Hodgkin's Lymphoma Treated With ABVD

BACKGROUND

Population-based studies on Hodgkin's lymphoma (HL) have shown reduced survival in Hispanics and non-Hispanic Blacks compared with non-Hispanic Whites. To better understand the factors contributing to this outcome discrepancy, we retrospectively reviewed the charts of patients with HL diagnosed and treated at a single institution located along the Texas-Mexico border.

PATIENTS AND METHODS

We performed a retrospective chart review of all patients with HL treated at our institution over an 8-year period (2011-2018). The International Prognostic Score was calculated for all patients and results of positron-emission tomography (PET) scans (interim and end of treatment) were also recorded. Variables analyzed included tumor-related findings (stage, subtype of HL), treatment history (chemotherapy regimen including number of cycles, dose intensity and radiation treatments) and neutrophil to lymphocyte ratio. Quantitative variables were described using median, interquartile range, minimum and maximum observations. Categorical variables were described using frequency and proportions. Kaplan-Meier curves were used to show relapse-free survival.

RESULTS

A total of 24 patients were treated in the time frame, of whom 23 were Hispanic. All were treated with doxorubicin, bleomycin, vinblastine and dacarbazine (ABVD) or an ABVD-like regimen. Dose intensity for chemotherapy exceeded 90%. After a median follow-up of 43 months, the relapse rate was 45.8%. Positive and negative predictive values for interim PET (0% and 50%) and end of therapy PET (80% and 58%) were suboptimal to allow for a PET-adapted therapeutic approach.

CONCLUSION

Hispanics have a high relapse rate following ABVD which is not fully explained by universally accepted prognostic factors. Performance of PET scan in predicting outcomes of HL needs to be further studied and optimized before adopting a PET-adapted treatment paradigm for underserved Hispanic populations.

ABVD (doxorubicin, bleomycin, vinblastine, dacarbazine) as front-line therapy for Hodgkins lymphoma in Hispanic patients: A single center experience from Texas-Mexico Border

e19514

Background: Population-based studies in Hodgkin Lymphoma (HL) have shown reduced survival in patients of Hispanic ethnicity as compared with non-Hispanic Whites. ABVD is the most commonly used regimen for HL in the United States. We retrospectively reviewed the charts of Hispanic patients with HL treated at a single institution located along the Texas-Mexico border. Methods: We performed a chart review of Hispanic patients with HL treated at our institution over an 8 year period. Prognostic (Stage, International Prognostic Score) and predictive (results of interim and end of therapy PET scan) factors were recorded. Relative dose intensity (RDI: fraction of drug dose administered to the standard dose) of each chemotherapy drug was calculated.Treatment delays and their causes were recorded. Quantitative variables were described using median, inter-quartile range, minimum and maximum observations. Categorical variables were described using frequency and proportions. Kaplan – Meier curves were used to show relapse-free survival. Results: Base line characteristics are shown in table. A total of 24 patients were treated in the time frame of whom 45% were dependent on charity care. All were treated with ABVD or an ABVD-like regimen. After a median follow-up of 43 months, relapse rate for the entire cohort was 45.8%. ( 33.3% in early stage and 53.3% in advanced stage disease). Of the patients who relapsed 45% were unable to receive a stem cell transplant based salvage therapy. The RDI for each chemotherapy drug in ABVD was as follows: Doxorubicin (98.8%), Bleomycin (82.1%), vinblastine (97.9%) and dacarbazine (100%). The mean and median delay in completing chemotherapy was 9.9 and 5.5 days respectively (range 0-56). Conclusions: HL patients of Hispanic ethnicity have a high relapse rate with ABVD despite optimal delivery of the regimen. As medically underserved minority patients face significant barriers in accessing stem cell rescue based salvage treatments, decreasing the relapse rate with upfront therapy can help in addressing the disparity seen in survival. Non ABVD regimens shown to have a higher upfront remission rate like escalated dose BEACOPP (bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, prednisone) or A-AVD (brentuximab vedotin, doxorubicin, vinblastine, dacarbazine) should be studied in these patients.[Table: see text]

Mastocytosis

OBJECTIVES

The 2019 Workshop of the Society for Hematopathology/European Association for Haematopathology received and reviewed cases covering the spectrum of mastocytosis and related diseases, including morphologic mimics, focusing on recent updates and relevant findings for pathologists.

METHODS

The workshop panel reviewed 99 cases of cutaneous and systemic mastocytosis (SM) and SM and associated hematologic neoplasms (SM-AHN).

RESULTS

Despite a common theme of KIT mutation (particularly D816V), mastocytosis is a heterogeneous neoplasm with a wide variety of presentations. This spectrum, including rare subtypes and extramedullary organ involvement, is discussed and illustrated by representative cases.

CONCLUSIONS

In the age of targeted treatment aimed at KIT, the accurate diagnosis and classification of mastocytosis has major implications for therapy and further interventions. Understanding the clinical, pathologic, and genetic findings of mastocytosis is crucial for selecting the proper tests to perform and subsequent arrival at a correct diagnosis in this rare disease.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Myeloid/Lymphoid Neoplasms Associated With Eosinophilia and Rearrangements of PDGFRA, PDGFRB, or FGFR1 or With PCM1-JAK2

OBJECTIVES

To summarize cases submitted to the 2019 Society for Hematopathology/European Association for Haematopathology Workshop under the category of myeloid/lymphoid neoplasms with eosinophilia and PDGFRA, PDGFRB, or FGFR1 or with PCM1-JAK2 rearrangements, focusing on recent updates and relevant practice findings.

METHODS

The cases were summarized according to their respective gene rearrangement to illustrate the spectrum of clinical, laboratory, and histopathology manifestations and to explore the appropriate molecular genetic tests.

RESULTS

Disease presentations were heterogeneous, including myeloproliferative neoplasms (MPNs), myelodysplastic syndromes (MDSs), MDS/MPN, acute myeloid leukemia, acute B- or T-lymphoblastic lymphoma/acute lymphoblastic lymphoma (ALL/LBL), or mixed-lineage neoplasms. Frequent extramedullary involvement occurred. Eosinophilia was common but not invariably present. With the advancement of RNA sequencing, cryptic rearrangements were recognized in genes other than PDGFRA. Additional somatic mutations were more frequent in the FGFR1-rearranged cases. Cases with B-ALL presentations differed from Philadelphia-like B-ALL by the presence of an underlying MPN. Cases with FLT3 and ABL1 rearrangements could be potential candidates for future inclusion in this category.

CONCLUSIONS

Accurate diagnosis and classification of this category of myeloid/lymphoid neoplasms has important therapeutic implications. With the large number of submitted cases, we expand our understanding of these rare neoplasms and improve our ability to diagnose these genetically defined disorders.