More than 1 TP53 abnormality is a dominant characteristic of pure erythroid leukemia

Fifth edition WHO classification: myeloid neoplasms

The fifth edition of the WHO classification of haematolymphoid tumours (WHO-HEM5) introduces significant advancements in the understanding and diagnosis of myeloid neoplasms, emphasising molecular and genetic insights. This review highlights key updates from the revised fourth edition (WHO-HEM4R), particularly the integration of genetic criteria for disease classification. Many entities are now defined by specific genetic abnormalities, enhancing diagnostic precision and prognostic assessment. Notably, the elimination of the 20% blast threshold for acute myeloid leukaemia (AML) with specific defining genetic alterations reflects a shift towards genomic-driven diagnostics. Additional updates include the refined subclassification of myelodysplastic neoplasms (MDS) and MDS/myeloproliferative neoplasms, as well as the recognition of novel entities such as clonal haematopoiesis and MDS with biallelic TP53 inactivation, further expanding the spectrum of myeloid neoplasms. WHO-HEM5 illustrates the diagnostic utility of morphology, flow cytometry, immunohistochemistry and next-generation sequencing in resource-rich settings. However, its implementation in low-income and middle-income countries (LMICs) remains challenging due to limited access to advanced diagnostic tools. This review explores strategies to optimise diagnosis in resource-constrained environments, where morphology and immunophenotyping remain fundamental. By integrating molecular diagnostics with traditional methods, WHO-HEM5 aims to refine classification and facilitate risk stratification in the era of personalised medicine, providing haematopathologists and clinicians with an essential framework to navigate the complexities of myeloid neoplasms. The emphasis on advancing haematopathology practices worldwide, including in LMICs, demonstrates the ongoing commitment to improving global outcomes in haematological malignancies.

Erythroblastic Sarcoma in Adults and Children: Different Pathways to the Same Destination

Erythroblastic sarcoma (ES), the mass-forming presentation of acute erythroid leukemia, is a rare and challenging diagnosis. Given the limited number of published cases, the diagnostic criteria, immunophenotype, and molecular characteristics are not well defined. We describe 56 cases of ES (36 adult and 11 pediatric cases from our cohort, and 9 pediatric cases from the literature). The median age was 60 years among adults and 1.8 years among children. An association with prior cytotoxic therapy or myeloid neoplasm was documented in 10/36 (28%) and 25/36 (69%) adults, respectively, but was not reported in children. Bones were the most common site of involvement among adults (16/36, 44%), whereas soft tissue or central nervous system involvement was most common among children (each 9/20, 45%). Adult and pediatric ES shared similar morphologic features with all cases showing mass formation of erythroblasts and/or involvement of body fluids. Immunophenotypic analysis showed that blasts were positive for CD71 (49/49, 100%), GLUT1 (12/12, 100%), CD43 (37/39, 95%), E-cadherin (38/44, 86%), and CD117 (39/51, 76%) but were mostly negative for CD45 (15/48, 31% positive). Strong and diffuse P53 expression was common among adults (21/24, 88%) and absent among children (3/10, 30% with dim/subset positivity). Although a complex karyotype was common in adult (15/17, 88%) and pediatric ES (8/12, 68%), TP53 mutations were exclusively seen in adult ES (17/19, 89%), at least 11 of which (65%) were biallelic. Instead, pediatric ES was enriched for gene fusions; specific fusions were identified in 10 cases, 7 of which involved NFIA rearrangement. The prognosis was poor among both age groups; 29/37 (78%) patients died from disease with a median overall survival of 3 months. Overall, these results show that adult and pediatric ES have overlapping morphologic and immunophenotypic features but distinct molecular profiles suggesting diverging pathogenesis.

Flow cytometry evaluation of acute myeloid leukemia minimal residual disease based on an understanding of the normal maturation patterns in the blast compartments

OBJECTIVE

Detection of minimal/measurable disease (MRD) in acute myeloid leukemia (AML) is critical for both clinical decision-making and prognostication, yet remains a challenge. Flow cytometry is a well-established method for MRD detection. Flow cytometric (FC) evaluation of MRD must consider a complex maturational pattern of normal hematopoietic development to separate normal from abnormal progenitors. Here, we offer an example of an interpretive approach based on a thorough understanding of stage- and lineage-specific hematopoietic maturation.

METHODS

We provide a comprehensive overview of blast maturation from early precursors (hematopoietic stem cells) to committed late-stage unilineage progenitors and commonly observed stage-specific abnormalities based on cases we have encountered in practice. We emphasize the importance of stage-specific comparisons for accurate MRD detection by flow cytometry.

RESULTS

The AML blasts almost invariably show abnormal phenotypes, and the phenotypes may evolve upon therapy. The detected phenotypes are necessarily confined to the target antigens included in the panel. It is therefore critical to evaluate a range of antigens to establish a specific stage/state of lineage commitment and detect potential common abnormalities. Moreover, enough cells must be acquired to allow for the detection of MRD at desired levels. Significant technical and analytical validation is critical.

CONCLUSIONS

Flow cytometry offers a powerful single-cell-based platform for MRD detection in AML, and the results have been proven critical for disease management. Leukemia-associated phenotype-informed difference from the normal approach presented in this review presents an analytical framework for sensitive and accurate MRD detection.

Future directions in myelodysplastic syndromes/neoplasms and acute myeloid leukaemia classification: from blast counts to biology

Myelodysplastic syndromes/neoplasms (MDS) and acute myeloid leukaemia (AML) are neoplastic haematopoietic cell proliferations that are diagnosed and classified based on a combination of morphological, clinical and genetic features. Specifically, the percentage of myeloblasts in the blood and bone marrow is a key feature that has historically separated MDS from AML and, together with several other morphological parameters, defines distinct disease entities within MDS. Both MDS and AML have recurrent genetic abnormalities that are increasingly influencing their definitions and subclassification. For example, in 2022, two new MDS entities were recognised based on the presence of SF3B1 mutation or bi-allelic TP53 abnormalities. Genomic information is more objective and reproducible than morphological analyses, which are subject to interobserver variability and arbitrary numeric cut-offs. Nevertheless, the integration of genomic data with traditional morphological features in myeloid neoplasm classification has proved challenging by virtue of its sheer complexity; gene expression and methylation profiling also can provide information regarding disease pathogenesis, adding to the complexity. New machine-learning technologies have the potential to effectively integrate multiple diagnostic modalities and improve on historical classification systems. Going forward, the application of machine learning and advanced statistical methods to large patient cohorts can refine future classifications by advancing unbiased and robust previously unrecognised disease subgroups. Future classifications will probably incorporate these newer technologies and higher-level analyses that emphasise genomic disease entities over traditional morphologically defined entities, thus promoting more accurate diagnosis and patient risk stratification.

Acute Myeloid Leukemia: Diagnosis and Evaluation by Flow Cytometry

With recent technological advances and significant progress in understanding the pathogenesis of acute myeloid leukemia (AML), the updated fifth edition WHO Classification (WHO-HAEM5) and the newly introduced International Consensus Classification (ICC), as well as the European LeukemiaNet (ELN) recommendations in 2022, require the integration of immunophenotypic, cytogenetic, and molecular data, alongside clinical and morphologic findings, for accurate diagnosis, prognostication, and guiding therapeutic strategies in AML. Flow cytometry offers rapid and sensitive immunophenotyping through a multiparametric approach and is a pivotal laboratory tool for the classification of AML, identification of therapeutic targets, and monitoring of measurable residual disease (MRD) post therapy. The association of immunophenotypic features and recurrent genetic abnormalities has been recognized and applied in informing further diagnostic evaluation and immediate therapeutic decision-making. Recently, the evolving role of machine learning models in assisting flow cytometric data analysis for the automated diagnosis and prediction of underlying genetic alterations has been illustrated.

SOHO State of the Art Updates and Next Questions-WHO Classification of Acute Myeloid Leukemia

The 5th edition of the World Health Organization (WHO) classification of Hematolymphoid tumors provides a hierarchically-driven catalog of hematologic neoplasms and introduces a series of changes to the classification of acute myeloid leukemia (AML). Emphasizing molecular genetic findings, it expands the category of "acute myeloid leukemias with defining genetic abnormalities" while retaining the morphologically defined category of AML for cases that do not harbor disease-defining genetic drivers. The updates to the classification of AML provide refined definitions and diagnostic criteria based on clinicopathologic parameters and molecular genetic findings, emphasizing therapeutically and/or prognostically actionable biomarkers. This review provides an overview of the WHO 5th classification for AML with practical considerations for applying this classification system.

A rare case report of hemophagocytic lymphohistiocytosis secondary to pure eythroid leukemia in a person living with HIV

Pure erythroid leukemia (AML-M6) is a rare variant of acute myeloid leukemia (AML) with predominant erythroid lineage proliferation. The incidence of AIDS defining cancers including Kaposi sarcoma and non-Hodgkins lymphoma are on declining trends due to effective use of HAART (Highly Active Antiretroviral Therapy). Correspondingly, there have been increasing cases of leukemia in persons living with HIV. Our case is a 43 years old male living with HIV who was admitted with high grade fever and mucosal bleeds. On examination, he had periorbital swelling and ecchymosis with hepatosplenomegaly. The laboratory investigations revealed bicytopenia with high ferritin, low fibrinogen and hypertriglyceridemia. A diagnosis of hemophagocytic lymphohistiocytosis (HLH) with H score of 222 was made. Bone marrow examination revealed hypercellular marrow with more than 80% cells of erythroid lineage with 47% proerythroblasts. Suggesting pure erythroid leukemia (AML-M6). This diagnosis with secondary HLH carries a very poor prognosis in persons living with HIV.

An unusual case of pure erythroid leukemia with normal karyotype and NPM1 mutation

Pure erythroid leukemia (PEL) is an extremely rare subtype of acute myeloid leukemia (AML). Although not specific, PEL is almost uniformly associated with complex karyotype and TP53 mutations. Given the rarity of the disease, our understanding of its cytogenetic and molecular features deems incomplete. We aim to complement existing literature by presenting an unusual case of PEL. The case is comprehensively worked up with multiple modalities. We present for the first time a case of PEL with unusual cytogenetic and molecular features: normal karyotype with absence of TP53 mutations and presence of NPM1 and NRAS mutations. This is a valuable addition to literature, expanding our understanding of molecular and cytogenetic spectra of PEL.

A real-world analysis of clinical outcomes in AML with myelodysplasia-related changes: a comparison of ICC and WHO-HAEM5 criteria

ABSTRACT

The proposed fifth edition of the World Health Organization classification of hematolymphoid tumors (WHO-HAEM5) and International Consensus Classification (ICC) provide different definitions of acute myeloid leukemia with myelodysplasia-related genetics (AML-MR). We conducted a retrospective study which included a cohort of 432 patients, with 354 patients fulfilling WHO-HAEM5 criteria for WHO-AML-MR or 276 patients fulfilling ICC criteria for ICC-AML-MR by gene mutation or cytogenetics (ICC-AML-MR-M/CG). The clinicopathological features were largely similar, irrespective of the classification used, except for higher rates of complex karyotype, monosomy 17, TP53 mutations, and fewer RUNX1 mutations in the WHO-AML-MR group. TP53 mutations were associated with distinct clinicopathological features and dismal outcomes (hazard ratio [HR], 2.98; P < .001). ICC-AML-MR-M/CG group had superior outcome compared with the WHO-AML-MR group (HR, 0.80, P = .032), largely in part due to defining TP53 mutated AML as a standalone entity. In the intensively-treated group, WHO-AML-MR had significantly worse outcomes than AML by differentiation (HR, 1.97; P = .024). Based on ICC criteria, ICC-AML-MR-M/CG had more inferior outcomes compared to AML not otherwise specified (HR, 2.11; P = .048 and HR, 2.55; P = .028; respectively). Furthermore, changing the order of genetic abnormalities defining AML-MR (ie, by gene mutations or cytogenetics) did not significantly affect clinical outcomes. ICC-AML-MR-M/CG showed similar outcomes regardless of the order of assignment. We propose to harmonize the 2 classifications by excluding TP53 mutations from WHO-HAEM5 defined AML-MR group and combining AML-MR defined by gene mutations and cytogenetics to form a unified group.

Fifth Edition of the World Health Classification of Tumors of the Hematopoietic and Lymphoid Tissue: Myeloid Neoplasms

In this manuscript, we review myeloid neoplasms in the fifth edition of the World Health Organization classification of hematolymphoid tumors (WHO-HEM5), focusing on changes from the revised fourth edition (WHO-HEM4R). Disease types and subtypes have expanded compared with WHO-HEM4R, mainly because of the expansion in genomic knowledge of these diseases. The revised classification is based on a multidisciplinary approach including input from a large body of pathologists, clinicians, and geneticists. The revised classification follows a hierarchical structure allowing usage of family (class)-level definitions where the defining diagnostic criteria are partially met or a complete investigational workup has not been possible. Overall, the WHO-HEM5 revisions to the classification of myeloid neoplasms include major updates and revisions with increased emphasis on genetic and molecular drivers of disease. The most notable changes have been applied to the sections of acute myeloid leukemia and myelodysplastic neoplasms (previously referred to as myelodysplastic syndrome) with incorporation of novel, disease-defining genetic changes. In this review we focus on highlighting the updates in the classification of myeloid neoplasms, providing a comparison with WHO-HEM4R, and offering guidance on how the new classification can be applied to the diagnosis of myeloid neoplasms in routine practice.

Survival after Pure (Acute) Erythroid Leukemia in the United States: A SEER-Based Study

BACKGROUND

Acute erythroid leukemia (AEL), also known as pure erythroid leukemia, is a rare subtype of acute myeloid leukemia (AML) characterized by the proliferation of malignant erythroid precursors. Outcome data at the population level are scarce.

METHODS

We performed a retrospective analysis of the Surveillance Epidemiology and End Results (SEER) database. All cases with a histologically confirmed diagnosis of acute (pure) erythroid leukemia during the period of 2000-2019 were included in the study. The Kaplan-Meier method was used to perform survival analysis. The significance of differences between overall survival (OS) was analyzed using the log-rank test.

RESULTS

In total, 968 patients were included in the study. The median age was 68 years (range 0-95), 62% of patients were males, and 62.5% (n = 605) were treated with chemotherapy. The median OS for <18, 18-49, 50-64, 65-79 and 80+ age groups was 69, 18, 8, 3 and 1 month, respectively (p < 0.0001). Patients who received chemotherapy had significantly improved OS compared to patients who did not, among both adults (p < 0.0001) and children (p = 0.004). There were no significant differences in OS based on sex, race, ethnicity and median household income. Median OS for adults diagnosed in 2000-2004, 2005-2009, 2010-2014, 2015-2019 was 4, 6, 6 and 3 months, respectively, with no significant differences in OS between these groups.

CONCLUSION

AEL occurs in all age groups but is most common in the elderly. Outcomes are poor with current chemotherapeutic agents, with no improvement in the last two decades. This study stresses the urgent need for investigational agents.

TP53-Mutated Myelodysplasia and Acute Myeloid Leukemia

TP53-mutated myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) form a distinct and heterogeneous group of myeloid malignancies associated with poor outcomes. Studies carried out in the last years have in part elucidated the complex role played by TP53 mutations in the pathogenesis of these myeloid disorders and in the mechanisms of drug resistance. A consistent number of studies has shown that some molecular parameters, such as the presence of a single or multiple TP53 mutations, the presence of concomitant TP53 deletions, the association with co-occurring mutations, the clonal size of TP53 mutations, the involvement of a single (monoallelic) or of both TP53 alleles (biallelic) and the cytogenetic architecture of concomitant chromosome abnormalities are major determinants of outcomes of patients. The limited response of these patients to standard treatments, including induction chemotherapy, hypomethylating agents and venetoclax-based therapies and the discovery of an immune dysregulation have induced a shift to new emerging therapies, some of which being associated with promising efficacy. The main aim of these novel immune and nonimmune strategies consists in improving survival and in increasing the number of TP53-mutated MDS/AML patients in remission amenable to allogeneic stem cell transplantation.

The NFIA-ETO2 fusion blocks erythroid maturation and induces pure erythroid leukemia in cooperation with mutant TP53

The NFIA-ETO2 fusion is the product of a t(1;16)(p31;q24) chromosomal translocation, so far, exclusively found in pediatric patients with pure erythroid leukemia (PEL). To address the role for the pathogenesis of the disease, we facilitated the expression of the NFIA-ETO2 fusion in murine erythroblasts (EBs). We observed that NFIA-ETO2 significantly increased proliferation and impaired erythroid differentiation of murine erythroleukemia cells and of primary fetal liver-derived EBs. However, NFIA-ETO2-expressing EBs acquired neither aberrant in vitro clonogenic activity nor disease-inducing potential upon transplantation into irradiated syngenic mice. In contrast, in the presence of 1 of the most prevalent erythroleukemia-associated mutations, TP53R248Q, expression of NFIA-ETO2 resulted in aberrant clonogenic activity and induced a fully penetrant transplantable PEL-like disease in mice. Molecular studies support that NFIA-ETO2 interferes with erythroid differentiation by preferentially binding and repressing erythroid genes that contain NFI binding sites and/or are decorated by ETO2, resulting in a activity shift from GATA- to ETS-motif-containing target genes. In contrast, TP53R248Q does not affect erythroid differentiation but provides self-renewal and survival potential, mostly via downregulation of known TP53 targets. Collectively, our work indicates that NFIA-ETO2 initiates PEL by suppressing gene expression programs of terminal erythroid differentiation and cooperates with TP53 mutation to induce erythroleukemia.

Erythroleukemia: Classification

Acute erythroid leukemia (AEL) is a rare (2%-5%) form of acute myeloid leukemia (AML). Molecular alterations found in AEL resemble those of other AMLs. We report a classification of AELs in three major classes, with different prognosis and some specific features such as a tendency to mutual exclusion of mutations in epigenetic regulators and signaling genes.

Updates in molecular genetics of acute myeloid leukemia

Acute myeloid leukemia (AML) is a type of cancer caused by aggressive neoplastic proliferations of immature myeloid cells that is fatal if untreated. AML accounts for 1.0% of all new cancer cases in the United States, with a 5-year relative survival rate of 30.5%. Once defined primarily morphologically, advances in next generational sequencing have expanded the role of molecular genetics in categorizing the disease. As such, both the World Health Organization Classification of Haematopoietic Neoplasms and The International Consensus Classification System now define a variety of AML subsets based on mutations in driver genes such as NPM1, CEBPA, TP53, ASXL1, BCOR, EZH2, RUNX1, SF3B1, SRSF2, STAG2, U2AF1, and ZRSR2. This article provides an overview of some of the genetic mutations associated with AML and compares how the new classification systems incorporate molecular genetics into the definition of AML.

The fifth edition of the World Health Organization Classification and the International Consensus Classification of myeloid neoplasms: evolving guidelines in the molecular era with practical implications

PURPOSE OF REVIEW

There have been major advances in our understanding of molecular pathogenesis of myeloid neoplasms, which prompt the updates in the classification of myeloid neoplasms in the fifth edition of World Health Organization Classification (WHO-5) and the new International Consensus Classification (ICC). The purpose of this review is to provide an overview of these two classification systems for myeloid neoplasms.

RECENT FINDINGS

The definition, classification, and diagnostic criteria in many myeloid entities have been refined in WHO-5 and ICC with improved understanding of morphology and integration of new genetic findings. Particularly, molecular and cytogenetic studies have been increasingly incorporated into the classification, risk stratification, and selection of therapy of myeloid neoplasms. Overall, despite some revisions and discrepancies between WHO-5 and ICC, the major categories of myeloid neoplasms remain the same. Further validation studies are warranted to fine-tune and, ideally, integrate these two classifications.

SUMMARY

Integration of clinical information, laboratory parameters, morphologic features, and cytogenetic and molecular studies is essential for the classification of myeloid neoplasms, as recommended by both WHO-5 and ICC.

Comparison of the International Consensus and 5th WHO edition classifications of adult myelodysplastic syndromes and acute myeloid leukemia

Several editions of the World Health Organization (WHO) classifications of lympho-hemopoietic neoplasms in 2001, 2008, and 2016 served as the international standard for diagnosis. Since the 4th WHO edition, here referred as WHO-HAEM4, significant clinico-pathological, immunophenotypic, and molecular advances have been made in the field of myeloid neoplasms, which have contributed to refine diagnostic criteria, to upgrade entities previously defined as provisional and to identify new entities. This process has resulted in two recent classification proposals of myeloid neoplasms: the International Consensus Classification (ICC) and the 5th edition of the WHO classification (WHO-HAEM5). In this paper, we review and compare the two classifications in terms of diagnostic criteria and entity definition, with a focus on adult myelodysplastic syndromes/neoplasms (MDS) and acute myeloid leukemia (AML). The goal is to provide a tool to facilitate the work of pathologists, hematologists and researchers involved in the diagnosis and treatment of these hematological malignancies.

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.

Emerging bone marrow failure syndromes- new pieces to an unsolved puzzle

Inherited bone marrow failure (BMF) syndromes are genetically diverse - more than 100 genes have been associated with those syndromes and the list is rapidly expanding. Risk assessment and genetic counseling of patients with recently discovered BMF syndromes is inherently difficult as disease mechanisms, penetrance, genotype-phenotype associations, phenotypic heterogeneity, risk of hematologic malignancies and clonal markers of disease progression are unknown or unclear. This review aims to shed light on recently described BMF syndromes with sparse concise data and with an emphasis on those associated with germline variants in ADH5/ALDH2, DNAJC21, ERCC6L2 and MECOM. This will provide important data that may help to individualize and improve care for these patients.

TP53-Mutated Myelodysplastic Syndrome and Acute Myeloid Leukemia: Biology, Current Therapy, and Future Directions

TP53-mutated myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) form a distinct group of myeloid disorders with dismal outcomes. TP53-mutated MDS and AML have lower response rates to either induction chemotherapy, hypomethylating agent-based regimens, or venetoclax-based therapies compared with non-TP53-mutated counterparts and a poor median overall survival of 5 to 10 months. Recent advances have identified novel pathogenic mechanisms in TP53-mutated myeloid malignancies, which have the potential to improve treatment strategies in this distinct clinical subgroup. In this review, we discuss recent insights into the biology of TP53-mutated MDS/AML, current treatments, and emerging therapies, including immunotherapeutic and nonimmune-based approaches for this entity.

SIGNIFICANCE

Emerging data on the impact of cytogenetic aberrations, TP53 allelic burden, immunobiology, and tumor microenvironment of TP53-mutated MDS and AML are further unraveling the complexity of this disease. An improved understanding of the functional consequences of TP53 mutations and immune dysregulation in TP53-mutated AML/MDS coupled with dismal outcomes has resulted in a shift from the use of cytotoxic and hypomethylating agent-based therapies to novel immune and nonimmune strategies for the treatment of this entity. It is hoped that these novel, rationally designed combinations will improve outcomes in this area of significant unmet need.

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.

Flow cytometry immunophenotypic features of pure erythroid leukemia and the distinction from reactive erythroid precursors

BACKGROUND

The immunophenotype of pure erythroid leukemia (PEL) as determined by flow cytometry immunophenotypic analysis is not well characterized. The immunophenotypic difference between PEL and reactive conditions is under-explored.

METHODS

We assessed and compared the immunophenotype of 24 PEL cases and 28 reactive cases containing early erythroid precursors by flow cytometry.

RESULTS

The neoplastic erythroid cells in all PEL cases were positive for CD36 and CD71. CD45 was also positive in all cases, but the expression level was often dimmer than granulocytes. CD117 expression ranged from partial to uniform, and CD235a was often only positive in the CD117-dim to negative cells, corresponding to more differentiated subset. PEL cases frequently (87%) showed decreased or negative CD38 expression, contrasting to reactive early erythroid precursors that showed bright CD38 (p < 0.0001). CD7 (25%) and CD13 (29%) aberrant expressions were only observed in PEL but not in the reactive erythroid cells. Normal early erythroid precursors in all reactive bone marrows showed partial expression of CD4; In contrast, aberrant CD4 expression was detected in 71% PEL cases, either uniformly positive (50%) or completely negative (21%). While normal/reactive bone marrows almost always contained a small subset of CD34-positive early erythroid precursors, the neoplastic pronormoblasts in all PEL cases were CD34 negative. Although not increased in number, CD34-positive myeloblasts were frequently detected in PEL and demonstrated an aberrant immunophenotype in 90% PEL cases.

CONCLUSIONS

PEL shows a distinctive immunophenotype which can be distinguished from reactive erythroid precursors by flow cytometry immunophenotyping.

Clinical Outcomes of Acute Myeloid Leukemia Patients Harboring the RUNX1 Mutation: Is It Still an Unfavorable Prognosis? A Cohort Study and Meta-Analysis

Acute myeloid leukemia (AML) with mutated RUNX1 (RUNX1mut) is considered to have an unfavorable prognosis. However, recent studies have reported comparable survival outcomes with wild-type RUNX1 (RUNX1wt). To assess the clinical outcomes of AML with and without RUNX1mut, we performed a prospective cohort study and systematic review and meta-analysis. The study enrolled 135 patients (27 with RUNX1mut; 108 with RUNX1wt). There were no significant differences in the median OS and RFS of the RUNX1mut and RUNX1wt groups (9.1 vs. 12.2 months; p = 0.268 and 7.8 vs. 14.6 months; p = 0.481, respectively). A subgroup analysis of de novo AML patients with intermediate-risk cytogenetics showed similar outcomes. Our meta-analysis pooled data from 23 studies and our study. The complete remission rate was significantly lower in the RUNX1mut group (pooled odds ratio: 0.42). The OS, RFS, and event-free survival rates also favored the RUNX1wt group (pooled risk ratios: 1.36, 1.37, and 1.37, respectively). A subgroup analysis of de novo AML patients with intermediate-risk cytogenetics demonstrated nearly identical OS and RFS outcomes. This study confirms that patients with AML and RUNX1mut had poor prognoses. Nonetheless, in de novo AML with intermediate-risk cytogenetics, the survival outcomes of both groups were comparable.

Diagnosis and management of AML in adults: 2022 recommendations from an international expert panel on behalf of the ELN

The 2010 and 2017 editions of the European LeukemiaNet (ELN) recommendations for diagnosis and management of acute myeloid leukemia (AML) in adults are widely recognized among physicians and investigators. There have been major advances in our understanding of AML, including new knowledge about the molecular pathogenesis of AML, leading to an update of the disease classification, technological progress in genomic diagnostics and assessment of measurable residual disease, and the successful development of new therapeutic agents, such as FLT3, IDH1, IDH2, and BCL2 inhibitors. These advances have prompted this update that includes a revised ELN genetic risk classification, revised response criteria, and treatment recommendations.

Amplified EPOR/JAK2 Genes Define a Unique Subtype of Acute Erythroid Leukemia

Acute erythroid leukemia (AEL) is a unique subtype of acute myeloid leukemia characterized by prominent erythroid proliferation whose molecular basis is poorly understood. To elucidate the underlying mechanism of erythroid proliferation, we analyzed 121 AEL using whole-genome, whole-exome, and/or targeted-capture sequencing, together with transcriptome analysis of 21 AEL samples. Combining publicly available sequencing data, we found a high frequency of gains and amplifications involving EPOR/JAK2 in TP53-mutated cases, particularly those having >80% erythroblasts designated as pure erythroid leukemia (10/13). These cases were frequently accompanied by gains and amplifications of ERG/ETS2 and associated with a very poor prognosis, even compared with other TP53-mutated AEL. In addition to activation of the STAT5 pathway, a common feature across all AEL cases, these AEL cases exhibited enhanced cell proliferation and heme metabolism and often showed high sensitivity to ruxolitinib in vitro and in xenograft models, highlighting a potential role of JAK2 inhibition in therapeutics of AEL.

SIGNIFICANCE

This study reveals the major role of gains, amplifications, and mutations of EPOR and JAK2 in the pathogenesis of pure erythroleukemia. Their frequent response to ruxolitinib in patient-derived xenograft and cell culture models highlights a possible therapeutic role of JAK2 inhibition for erythroleukemia with EPOR/JAK2-involving lesions. This article is highlighted in the In This Issue feature, p. 369.

DNA repair in lung cancer: a large-scale quantitative analysis for polymorphisms in DNA repairing pathway genes and lung cancer susceptibility

BACKGROUND

The results of associations between single nucleotide polymorphisms (SNPs) of genes in DNA repairing pathway and lung cancer (LC) risk are inconsistent.

METHODS

We applied allele, dominant and recessive models to explore the risk of researched variants to LC in total LC and subgroups by ethnicity or LC subtypes with a cutoff point of p < 0.05.

RESULTS

A total of 76,935 cases and 88,649 controls from 192 articles were included. Among the analyzed 40 variants from 20 genes, we found 9 statistically significant variants in overall populations by allele model, including five SNPs (rs1760944, rs9344, rs13181, rs1001581, and rs915927) increasing LC risk (odd ratios [ORs] = 1.10-1.71) and four SNPs (rs1042522, rs3213245, rs11615, and rs238406) decreasing the risk (ORs = 0.75-0.94). We identified rs1042522 and rs13181 as significant variants for LC in three models. Additionally, we identified differential significant SNPs in ethnic and subtype's analysis with comparison to total population.

CONCLUSIONS

There are five SNPs in DNA repairing pathway associated with increased LC risk and four others decreased LC risk. Besides, the risky SNPs in different ethnicities and various LC subtypes were partly different, and the contribution of different genotypes to risk alleles were various as well.

BMP2/SMAD pathway activation in JAK2/p53-mutant megakaryocyte/erythroid progenitors promotes leukemic transformation

Leukemic transformation (LT) of myeloproliferative neoplasm (MPN) has a dismal prognosis and is largely fatal. Mutational inactivation of TP53 is the most common somatic event in LT; however, the mechanisms by which TP53 mutations promote LT remain unresolved. Using an allelic series of mouse models of Jak2/Trp53 mutant MPN, we identify that only biallelic inactivation of Trp53 results in LT (to a pure erythroleukemia [PEL]). This PEL arises from the megakaryocyte-erythroid progenitor population. Importantly, the bone morphogenetic protein 2/SMAD pathway is aberrantly activated during LT and results in abnormal self-renewal of megakaryocyte-erythroid progenitors. Finally, we identify that Jak2/Trp53 mutant PEL is characterized by recurrent copy number alterations and DNA damage. Using a synthetic lethality strategy, by targeting active DNA repair pathways, we show that this PEL is highly sensitive to combination WEE1 and poly(ADP-ribose) polymerase inhibition. These observations yield new mechanistic insights into the process of p53 mutant LT and offer new, clinically translatable therapeutic approaches.

The 5th edition of the World Health Organization Classification of Haematolymphoid Tumours: Myeloid and Histiocytic/Dendritic Neoplasms

The upcoming 5th edition of the World Health Organization (WHO) Classification of Haematolymphoid Tumours is part of an effort to hierarchically catalogue human cancers arising in various organ systems within a single relational database. This paper summarizes the new WHO classification scheme for myeloid and histiocytic/dendritic neoplasms and provides an overview of the principles and rationale underpinning changes from the prior edition. The definition and diagnosis of disease types continues to be based on multiple clinicopathologic parameters, but with refinement of diagnostic criteria and emphasis on therapeutically and/or prognostically actionable biomarkers. While a genetic basis for defining diseases is sought where possible, the classification strives to keep practical worldwide applicability in perspective. The result is an enhanced, contemporary, evidence-based classification of myeloid and histiocytic/dendritic neoplasms, rooted in molecular biology and an organizational structure that permits future scalability as new discoveries continue to inexorably inform future editions.

Are We Moving the Needle for Patients with TP53-Mutated Acute Myeloid Leukemia?

The currently available therapeutic options for patients with TP53-mutated acute myeloid leukemia (AML) are insufficient, as they translate to a median overall of only 6-9 months, and less than 10% of patients undergoing the most aggressive treatments, such as intensive induction therapy and allogeneic hematopoietic stem cell transplantation, will be cured. The lack of clear differences in outcomes with different treatments precludes the designation of a standard of care. Recently, there has been growing attention on this critical area of need by way of better understanding the biology of TP53 alterations and the disparities in outcomes among patients in this molecular subgroup, reflected in the development and testing of agents with novel mechanisms of action. Promising preclinical and efficacy data exist for therapies that are directed at the p53 protein rendered dysfunctional via mutation or that inhibit the CD47/SIRPα axis or other immune checkpoints such as TIM-3. In this review, we discuss recently attractive and emerging therapeutic agents, their preclinical rationale and the available clinical data as a monotherapy or in combination with the currently accepted backbones in frontline and relapsed/refractory settings for patients with TP53-mutated AML.

Novel t(1;8)(p31.3;q21.3) NFIA-RUNX1T1 Translocation in an Infant Erythroblastic Sarcoma

OBJECTIVES

Pure erythroid leukemia (PEL) is exceptionally rare in the pediatric setting. Four pediatric PEL cases with t(1;16)(p31;q24) NFIA-CBFA2T3 were reported previously. We present a case of an infant with PEL presenting with erythroblastic sarcoma and harboring a novel t(1;8)(p31.3;q21.3) NFIA-RUNX1T1 fusion detected by RNA sequencing and conventional karyotype.

METHODS

Bone marrow (BM) and abdominal mass biopsies from the patient were evaluated with extensive immunohistochemical, flow cytometric, cytogenetic, and molecular studies.

RESULTS

The patient was a female infant who presented between 2 and 5 months of age with cytopenias and an enlarging abdominal mass. Blasts in the BM and abdominal mass expressed CD71 and CD117 with focal expression of CD43, E-cadherin, epithelial membrane antigen, and hemoglobin A. They were negative for additional myeloid, lymphoid, and nonhematolymphoid markers. These findings were most consistent with PEL and erythroblastic sarcoma. RNA sequencing revealed the novel NFIA-RUNX1T1 fusion.

CONCLUSIONS

Along with the previously reported PELs with NFIA-CBFA2T3 fusions, we describe a subset of PELs that occur in children, that frequently display extramedullary disease, and that harbor rearrangements of NFIA with core binding factor genes. We hypothesize that, together, these cases represent a rare but distinct clinicopathologic group of pediatric PELs with recurrent genetic abnormality.

Molecular Landscapes and Models of Acute Erythroleukemia

Malignancies of the erythroid lineage are rare but aggressive diseases. Notably, the first insights into their biology emerged over half a century ago from avian and murine tumor viruses-induced erythroleukemia models providing the rationale for several transgenic mouse models that unraveled the transforming potential of signaling effectors and transcription factors in the erythroid lineage. More recently, genetic roadmaps have fueled efforts to establish models that are based on the epigenomic lesions observed in patients with erythroid malignancies. These models, together with often unexpected erythroid phenotypes in genetically modified mice, provided further insights into the molecular mechanisms of disease initiation and maintenance. Here, we review how the increasing knowledge of human erythroleukemia genetics combined with those from various mouse models indicate that the pathogenesis of the disease is based on the interplay between signaling mutations, impaired TP53 function, and altered chromatin organization. These alterations lead to aberrant activity of erythroid transcriptional master regulators like GATA1, indicating that erythroleukemia will most likely require combinatorial targeting for efficient therapeutic interventions.

Erythroleukemia: an Update

PURPOSE OF THE REVIEW

Acute erythroleukemia (AEL) is a rare form of acute myeloid leukemia recognized by erythroblastic proliferation. Many controversies remain around diagnosis influencing prognostic and therapeutic implications relating to this unique leukemia subset.

RECENT FINDINGS

The 2016 WHO classification includes more clear and restrictive diagnostic criteria for AEL. Primary acute erythroid leukemia is associated with complex and high-risk karyotypes including chromosomes 5q and 7q abnormalities. Mutational data shows that AEL is characterized by far lower NPM1 and FLT3-ITD mutation rates and higher mutational rates in TP53 compared with other AML subtypes. Hypomethylating agents have shown therapeutic value in AEL. In this article, we discuss the evolving diagnostic concepts of erythroleukemia, genomics, clinical outcome, and promising therapeutic targets through an appraisal of the current literature.

Pure erythroid leukemia subsequent to acute myelomonocytic leukemia: A case report

RATIONALE

Pure erythroid leukemia is a rare subcategory of acute myeloid leukemia characterized by predominant immature erythroid population. Its occurrence subsequent to acute myelomonocytic leukemia has not been reported before. We reported this rare case to call attention because it may pose a diagnostic challenge.

PATIENTS CONCERNS

A 54-year-old female patient presented to our hospital in March 2018 with symptoms of easy fatigability.

DIAGNOSIS

Bone marrow aspiration was hypercellular showing 67.2% blasts mainly including moderate myeloblasts and monoblasts. There was mild dysplasia with some cells having round, oval, or bizarre nuclei which containing 1 to 3 nucleolus. Erythroid lineage was hypoplasia and mature erythrocytes were generally normal. Conventional cytogenetics of bone marrow cells revealed complex karyotype (44, XX, del (5) (q14q34) del (5) (q14q34), del (14) t (11;14) (q10; q10), -16, del (17), -18[10]).

INTERVENTIONS

The patient was treated with second line chemotherapy but did not respond.

QUTCOMES

She died of cardiopulmonary failure 19days after starting of therapy.

LESSONS

This unexpected and relatively uncommon occurrence was associated with a universally rapid and fatal clinical course with survival measured in <2 months despite intensive chemotherapy. We call attention to this rare phenomenon because it may pose a diagnostic challenge.

Diagnosis of rare subtypes of acute myeloid leukaemia and related neoplasms

The diagnosis of acute myeloid leukaemia and related neoplasms in adults is challenging as this requires the integration of clinical findings, morphology, immunophenotype, cytogenetics, and molecular genetic findings. Lack of familiarity with rare subtypes of acute leukaemia hinders the diagnosis. In this review, we will describe diagnostic findings of several rare acute myeloid leukaemias and related neoplasms that primarily occur in adults including information on presentation, morphology, immunophenotype, genetics, differential diagnosis, and prognosis. Leukaemias discussed include blastic plasmacytoid dendritic cell neoplasm, acute myeloid leukaemia with t(6;9) (p23;q34.1); DEK-NUP214, acute myeloid leukaemia with inv(3)(q21.3q26.2) or t(3;3)(q21.3;q26.2); GATA2, MECOM, acute myeloid leukaemia with BCR-ABL1, acute leukaemias of ambiguous lineage, acute myeloid leukaemia with mutated RUNX1, pure erythroid leukaemia, acute panmyelosis with myelofibrosis, and acute basophilic leukaemia. Case studies with morphological features of the nine subtypes of acute myeloid leukaemia and related neoplasms have been included, and additional evidence available since publication of the 2016 World Health Organization Classification has been added to each subtype.

TP53 Mutations in Acute Myeloid Leukemia: Still a Daunting Challenge?

TP53 is a key tumor suppressor gene with protean functions associated with preservation of genomic balance, including regulation of cellular senescence, apoptotic pathways, metabolism functions, and DNA repair. The vast majority of de novo acute myeloid leukemia (AML) present unaltered TP53 alleles. However, TP53 mutations are frequently detected in AML related to an increased genomic instability, such as therapy‐related (t-AML) or AML with myelodysplasia-related changes. Of note, TP53 mutations are associated with complex cytogenetic abnormalities, advanced age, chemoresistance, and poor outcomes. Recent breakthroughs in AML research and the development of targeted drugs directed at specific mutations have led to an explosion of novel treatments with different mechanisms. However, optimal treatment strategy for patients harboring TP53 mutations remains a critical area of unmet need. In this review, we focus on the incidence and clinical significance of TP53 mutations in de novo and t-AML. The influence of these alterations on response and clinical outcomes as well as the current and future therapeutic perspectives for this hardly treatable setting are discussed.

p53 immunohistochemistry discriminates between pure erythroid leukemia and reactive erythroid hyperplasia

Pure erythroid leukemia (PEL) is a rare, aggressive subtype of acute myeloid leukemia with a poor prognosis. The diagnosis of PEL is often medically urgent, quite challenging, and is typically a diagnosis of exclusion requiring meticulous distinction from non-neoplastic erythroid proliferations, particularly florid erythroid hyperplasia/regeneration. Given the frequency of TP53 mutations in the molecular signature of PEL, we hypothesize that differential p53 expression by immunohistochemistry (IHC) may be useful in distinguishing PEL versus non-neoplastic erythroid conditions. We performed p53 IHC on 5 normal bone marrow, 46 reactive erythroid proliferations, and 27 PEL cases. We assessed the positivity and intensity of nuclear staining in pronormoblasts and basophilic normoblasts using a 0–3+ scale with 0 being absent (with internal positive controls) and 3 being strong nuclear positivity. A total of 26/27 PEL cases showed strong, uniform, diffuse intense staining by the neoplastic pronormoblasts versus 0/5 and 0/46 normal and reactive controls, respectively. The control cases show various staining patterns ranging from 0 to 3+ in scattered erythroid precursor cells. Uniform, strong p53 positivity is unique to PEL and discriminates this entity from a benign erythroid mimic. Thus, p53 IHC may be a useful marker in urgent medical cases to assist in the confirmation of a malignant PEL diagnosis while awaiting the results of additional ancillary studies such as cytogenetics.

Bcor deficiency perturbs erythro-megakaryopoiesis and cooperates with Dnmt3a loss in acute erythroid leukemia onset in mice

Recurrent loss-of-function mutations of BCL6 co-repressor (BCOR) gene are found in about 4% of AML patients with normal karyotype and are associated with DNMT3a mutations and poor prognosis. Therefore, new anti-leukemia treatments and mouse models are needed for this combinatorial AML genotype. For this purpose, we first generated a Bcor^-/- knockout mouse model characterized by impaired erythroid development (macrocytosis and anemia) and enhanced thrombopoiesis, which are both features of myelodysplasia/myeloproliferative neoplasms. We then created and characterized double Bcor^-/-/Dnmt3a^-/- knockout mice. Interestingly, these animals developed a fully penetrant acute erythroid leukemia (AEL) characterized by leukocytosis secondary to the expansion of blasts expressing c-Kit+ and the erythroid marker Ter119, macrocytic anemia and progressive reduction of the thrombocytosis associated with loss of Bcor alone. Transcriptomic analysis of double knockout bone marrow progenitors revealed that aberrant erythroid skewing was induced by epigenetic changes affecting specific transcriptional factors (GATA1-2) and cell-cycle regulators (Mdm2, Tp53). These findings prompted us to investigate the efficacy of demethylating agents in AEL, with significant impact on progressive leukemic burden and mice overall survival. Information gained from our model expands the knowledge on the biology of AEL and may help designing new rational treatments for patients suffering from this high-risk leukemia.

Human erythroleukemia genetics and transcriptomes identify master transcription factors as functional disease drivers

Acute erythroleukemia (AEL or acute myeloid leukemia [AML]-M6) is a rare but aggressive hematologic malignancy. Previous studies showed that AEL leukemic cells often carry complex karyotypes and mutations in known AML-associated oncogenes. To better define the underlying molecular mechanisms driving the erythroid phenotype, we studied a series of 33 AEL samples representing 3 genetic AEL subgroups including TP53-mutated, epigenetic regulator-mutated (eg, DNMT3A, TET2, or IDH2), and undefined cases with low mutational burden. We established an erythroid vs myeloid transcriptome-based space in which, independently of the molecular subgroup, the majority of the AEL samples exhibited a unique mapping different from both non-M6 AML and myelodysplastic syndrome samples. Notably, >25% of AEL patients, including in the genetically undefined subgroup, showed aberrant expression of key transcriptional regulators, including SKI, ERG, and ETO2. Ectopic expression of these factors in murine erythroid progenitors blocked in vitro erythroid differentiation and led to immortalization associated with decreased chromatin accessibility at GATA1-binding sites and functional interference with GATA1 activity. In vivo models showed development of lethal erythroid, mixed erythroid/myeloid, or other malignancies depending on the cell population in which AEL-associated alterations were expressed. Collectively, our data indicate that AEL is a molecularly heterogeneous disease with an erythroid identity that results in part from the aberrant activity of key erythroid transcription factors in hematopoietic stem or progenitor cells.

Pure Erythroid Leukemia in a Sickle Cell Patient Treated with Hydroxyurea

We present a very rare case of pure erythroid leukemia arising in a young patient with sickle cell disease being treated with hydroxyurea for almost 5 years. Diagnosing and managing this rare condition has been a challenge and the majority of patients with pure erythroid leukemia have a very poor prognosis with survival in months despite treatment. This form of leukemia could be therapy related and in our case, hydroxyurea may have been responsible for the development of this aggressive condition.

Functional Classification of TP53 Mutations in Acute Myeloid Leukemia

Mutations of the TP53 gene occur in a subset of patients with acute myeloid leukemia (AML) and confer an exceedingly adverse prognosis. However, whether different types of TP53 mutations exert a uniformly poor outcome has not been investigated yet. Here, we addressed this issue by analyzing data of 1537 patients intensively treated within protocols of the German-Austrian AML study group. We classified TP53 mutations depending on their impact on protein structure and according to the evolutionary action (EAp53) score and the relative fitness score (RFS). In 98/1537 (6.4%) patients, 108 TP53 mutations were detected. While the discrimination depending on the protein structure and the EAp53 score did not show a survival difference, patients with low-risk and high-risk AML-specific RFS showed a different overall survival (OS; median, 12.9 versus 5.5 months, p = 0.017) and event-free survival (EFS; median, 7.3 versus 5.2 months, p = 0.054). In multivariable analyses adjusting for age, gender, white blood cell count, cytogenetic risk, type of AML, and TP53 variant allele frequency, these differences were statistically significant for both OS (HR, 2.14; 95% CI, 1.15-4.0; p = 0.017) and EFS (HR, 1.97; 95% CI, 1.06-3.69; p = 0.033). We conclude that the AML-specific RFS is of prognostic value in patients with TP53-mutated AML and a useful tool for therapeutic decision-making.

Insertional mutagenesis using the Sleeping Beauty transposon system identifies drivers of erythroleukemia in mice

Insertional mutagenesis is a powerful means of identifying cancer drivers in animal models. We used the Sleeping Beauty (SB) transposon/transposase system to identify activated oncogenes in hematologic cancers in wild-type mice and mice that express a stabilized cyclin E protein (termed cyclin ET74AT393A). Cyclin E governs cell division and is misregulated in human cancers. Cyclin ET74AT393A mice develop ineffective erythropoiesis that resembles early-stage human myelodysplastic syndrome, and we sought to identify oncogenes that might cooperate with cyclin E hyperactivity in leukemogenesis. SB activation in hematopoietic precursors caused T-cell leukemia/lymphomas (T-ALL) and pure red blood cell erythroleukemias (EL). Analysis of >12,000 SB integration sites revealed markedly different oncogene activations in EL and T-ALL: Notch1 and Ikaros were most common in T-ALL, whereas ETS transcription factors (Erg and Ets1) were targeted in most ELs. Cyclin E status did not impact leukemogenesis or oncogene activations. Whereas most SB insertions were lost during culture of EL cell lines, Erg insertions were retained, indicating Erg's key role in these neoplasms. Surprisingly, cyclin ET74AT393A conferred growth factor independence and altered Erg-dependent differentiation in EL cell lines. These studies provide new molecular insights into erythroid leukemia and suggest potential therapeutic targets for human leukemia.

Clinical implications of subclonal TP53 mutations in acute myeloid leukemia

The role of subclonal TP53 mutations, defined by a variant allele frequency of <20%, has not been addressed in acute myeloid leukemia yet. We, therefore, analyzed their prognostic value in a cohort of 1,537 patients with newly diagnosed disease, prospectively treated within three trials of the "German-Austrian Acute Myeloid Leukemia Study Group". Mutational analysis was performed by targeted deep sequencing and patients with TP53 mutations were categorized by their variant allele frequency into groups with frequencies >40%, 20%-40% and <20%. A total of 108 TP53 mutations were found in 98 patients (6.4%). Among these, 61 patients had variant allele frequencies >40%, 19 had variant allele frequencies between 20%-40% and 18 had frequencies <20%. Compared to specimens with clonal TP53 mutations, those with subclonal ones showed significantly fewer complex karyotypes and chromosomal losses. In either TP53-mutated group, patients experienced significantly fewer complete responses (P<0.001) and had worse overall and event-free survival rates (P<0.0001). In Cox regression analyses adjusting for age, white blood cell count, cytogenetic risk and type of acute myeloid leukemia, the adverse prognostic effect of TP53 mutations remained significant for all TP53-mutated subgroups. These data suggest that subclonal TP53 mutations are a novel prognostic parameter in acute myeloid leukemia and emphasize the usefulness of next-generation sequencing technologies for risk stratification in this disorder. The study was registered at ClinicalTrials.gov with number NCT00146120.