Abstract
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.
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Introduction
Acute myeloid leukemia (AML) is a heterogeneous disease with a wide variety of clinical presentations, morphological features, and immunophenotypes. The revised 4th edition World Health Organization (WHO) classification of acute myeloid leukemia (AML), developed in 2016 and published in book form in 2017, recognized subtypes of AML based on clinical, morphologic, and genetic features [1]. The WHO AML classification has its origins in the morphologic French-American-British (FAB) classification, but evolved to define disease categories based on cytogenetic abnormalities, mutational profile, and patient history (prior MDS, MDS/MPN, MPN, or cytotoxic therapy), with a complex hierarchy of assigning each AML case to a unique disease category [2]. The specific subgroups included AML with recurrent genetic abnormalities, AML with myelodysplasia-related changes, therapy-related myeloid neoplasms, and AML, not otherwise specified. Each disease category within the AML group attempted to define entities with similar biologic features associated with similar patient outcomes. One of the goals of the recently developed International Consensus Classification (ICC) of acute leukemias was to move to a more genetically defined classification while working in collaboration with clinicians through the Clinical Advisory Committee (CAC) process [3]. The ICC AML classification has been informed by the rapid evolution of molecular genetics into an indispensable diagnostic discipline that has brought about major advances in our understanding of the molecular landscape of AML.
TP53 is one of the most frequently mutated genes across all cancer types. AML patients with TP53 mutations have a nearly uniformly poor prognosis, suggesting a biologically homogeneous single group, yet in the 2016 WHO classification were included under therapy-related AML (t-AML), AML not otherwise specified (AML-NOS), pure erythroid leukemia, and AML with myelodysplasia-related changes (AML-MRC) groups [1]. In the updated ICC classification, AML with mutated TP53 is now recognized as a separate single entity [3]. A history of prior therapy or progression from myelodysplastic syndrome (MDS) or a myelodysplastic/myeloproliferative neoplasm (MDS/MPN) is now applied as qualifiers to the diagnosis rather than as specific disease categories to reduce confusion caused by the substantial overlap of prior AML categories. The category of AML-MRC is eliminated. Most of the cases previously included in this subtype are now allocated to the new subgroups of AML with myelodysplasia-related cytogenetic abnormalities and AML with mutated TP53 and AML with myelodysplasia-related gene mutations.
A number of genetic abnormalities, many of which are a result of recurring chromosome abnormalities, are used to define distinct disease entities and in the prior WHO classification included three specific subtypes of AML that did not require a minimal blast percentage. These included AMLs with t(8;21)(q22;q22.1), inv(16)(p13.1q22), t(16;16)(p13.1;q22), and t(15;17)(q24;q21). The ICC expands the category that may be diagnosed as AML with < 20% blasts to encompass additional recurring genetic abnormalities and also NPM1 and in-frame bZIP CEBPA mutations and requires a blast count of ≥ 10%. The remaining AML subtypes retain the 20% or more blast requirement. MDS cases with 10–19% blasts are now diagnosed as MDS/AML, reflecting the diagnostic continuum between AML and MDS and clinical and genetic heterogeneity among individual patients with these lower blast counts.
AML with myelodysplasia-related gene mutations
Defined by mutations in ASXL1, BCOR, EZH2, RUNX1, SF3B1, SRSF2, STAG2, U2AF1, or ZRSR2
AML with myelodysplasia-related changes was an attempt to identify a subgroup of AML featuring older age, lower blast counts, lower remission rate, and shorter overall survival. In the 2016 WHO classification, the category of AML-MRC applied to patients with AML who have 20% or more blasts in the blood or bone marrow and who meet any of the following criteria: a history of MDS or MDS/MPN, such as chronic myelomonocytic leukemia (CMML); an MDS-related cytogenetic abnormality; or multilineage dysplasia in 50% or more of two or more cell lines in the absence of NPM1 or biallelic CEBPA mutations [1]. The classification of AML-MRC overlaps somewhat with the traditional term “secondary AML,” which includes patients with AML that develops from an antecedent hematologic disorder (including MDS and MDS/MPN), as well as those with therapy-related AML that develops after prior cytotoxic therapy, radiotherapy, or immunosuppressive therapy. The AML-MRC group included a variety of cytogenetic abnormalities, including complex karyotypes (defined as three or more unrelated abnormalities) and other specified unbalanced and balanced abnormalities and excluded cases of therapy-related AML and AML with recurrent genetic abnormalities, such as t(8;21), inv(3), and t(6;9), the latter two of which may have multilineage dysplasia [4]. Whether the presence of dysplastic morphologic features alone warrants classification into a group associated with a poor prognosis has been controversial and several studies showed conflicting results as to whether dysplastic morphology is independently prognostic or merely reflects underlying adverse cytogenetics and/or mutation profile [5,6,7,8,9]. Although not part of the 2016 disease definition, various gene mutations are more commonly associated with AML-MRC, including mutations of ASXL1, TP53, and U2AF1, and could have accounted for prognostic significance within this group.
In the past decade, next-generation sequencing (NGS) technology has expanded our understanding of AML and revealed common genetic mutations with important roles in pathogenesis and prognosis [10]. Based on these results, European Leukemia Net (ELN) incorporated NGS data to develop a risk stratification system used in AML management [11]. Lindsley et al. [12] found that the presence of a mutation in SRSF2, SF3B1, U2AF1, ZRSR2, ASXL1, EZH2, BCOR, or STAG2 was > 95% specific for the diagnosis of secondary AML. Papaemmanuil et al. [13] confirmed lower survival rates and higher relapse rates in patients with chromatin-spliceosome gene mutations (including SRSF2, ASXL1, STAG2) as compared to other subgroups. A lower response rate and worse survival were also described in patients with mutations in SRSF2, U2AF1, and ASXL1 by Gao et al. [14]. Baer et al. [15] identified a mutational pattern including SRSF2, U2AF1, SF3B1, ASXL1, EZH2, BCOR, and STAG2 that allowed to distinguish AML-MRC from non-AML-MRC patients. Overall survival was inferior in patients harboring these mutations, irrespective of whether they were classified as AML-MRC or not. Furthermore, the molecular AML-MRC-like pattern was identified in over 10% of patients not classified as MRC per WHO criteria but who experienced a similarly poor overall survival, suggesting the definition of AML-MRC should be expanded to include this molecularly determined subset as well. Based on this data, the ICC created this new category and eliminated AML-MRC defined solely by morphologic dysplasia and merged the prior category of AML with mutated RUNX1 into this group (Fig. 1). RUNX1 mutations in AML were already well known to be associated with prior therapy (especially radiation) and prior MDS [16, 17].
AML with myelodysplasia-related cytogenetic abnormalities
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Defined by detecting a complex karyotype (≥ 3 unrelated clonal chromosomal abnormalities in the absence of other class-defining recurring genetic abnormalities), del(5q)/t(5q)/add(5q), − 7/del(7q), + 8, del(12p)/t(12p)/add(12p), i(17q), − 17/add(17p) or del(17p), del(20q), or idic(X)(q13) clonal abnormalities
By definition, patients with a 2016 WHO diagnosis of AML-MRC have a high frequency of adverse cytogenetics, including complex karyotypes [18]. One study reported that 262 patients with AML included 57% who were 75 years or older, 53% had poor-risk cytogenetics, and approximately one-third were reported to have had antecedent MDS [19]. A separate study also identified antecedent MDS or MDS/MPN and de novo AML with MDS-related cytogenetics as conferring a worse prognosis compared with patients with AML-MRC who had a diagnosis based on multilineage dysplasia [20].
Rogers et al. [21] reported that most cases of AML-MRC were associated with adverse genetic abnormalities, particularly –5/del(5q), –7/del(7q), and/or complex karyotype (CK). The presence of a complex karyotype (CK), defined as ≥ 3 chromosomal abnormalities, comprises 10 to 12% of all acute myeloid leukemia (AML) patients and constitutes the second largest cytogenetic subset of AML patients (after those with normal karyotype). In the ELN classification, a complex karyotype is defined as three or more chromosomal abnormalities in the absence of the WHO-designated recurring translocations or inversions, such as t(8;21), inv(16) or t(16;16), t(9;11), t(v;11)(v;q23.3), t(6;9), inv(3), or t(3;3), whereas the UK National Cancer Research Institute Adult Leukemia Working Group requires four or more chromosomal abnormalities as an adverse risk factor [22]. Other studies have shown that AML with monosomal karyotype (MK) presented with a significantly worse overall survival, disease-free survival, and complete response rate and predominantly was subclassified as AML-MRC, suggesting MK as a possible stronger adverse prognostic factor than the traditionally defined CK [23,24,25]. This ICC category retains the prior unbalanced cytogenetic abnormalities of AML-MRC, but now adds + 8 and del(20q) for such subclassification because, in the context of an increase in blast cells, they are considered myelodysplasia-related even if they may occur in non-MDS settings when blast cells are not increased.
AML with recurrent genetic abnormalities
This group has been expanded to include additional variant translocations involving RARA, KMT2A, and MECOM and other genetically related entities (see Table 1 and Table 2). The number of blasts required for a diagnosis of AML in the presence of recurrent genetic abnormalities is ≥ 10% for the entire group with exception of AML with t(9;22)(q34.1;q11.2): the latter still requires at least 20% blasts to avoid potential overlap with the progression of chronic myeloid leukemia. Compared with patients with myeloid blast transformation of CML, patients with AML with t(9;22)(q34.1;q11.2) have less frequent splenomegaly, lower peripheral blood basophilia, and lower bone marrow cellularity and myeloid-to-erythroid ratio [26]. Despite these differences, some cases will only become apparent as blast transformation when they recur with the chronic phase of CML. Cases with < 10% blasts and PML::RARA, RUNX1::RUNXT1, and CBFB::MYH11 rearrangements are exceedingly rare. In such cases, careful attention should be paid to including blast equivalents in the blast count and confirming the cytogenetic findings, particularly if detected initially at a low level. Many of these cases likely represent early AML and could be treated as such if clinically indicated, particularly in the absence of MDS morphologic features. Patients with < 10% blasts and any of the other AML-associated genetic findings including KMT2A translocations, inv(3)/t(3;3), and CEBPA mutations should continue to be classified as MDS until further data can be accumulated as to the clinical behavior and optimal treatment approach of these rare cases. About 2% of APL cases are characterized by atypical rearrangements, where RARA is fused to partners other than PML or in which the translocation involves other members of the RAR superfamily. The MDS1/EVI1 complex (MECOM) is located on chromosome 3q26. EVI1 is a nuclear transcription factor and represents a proto-oncogene playing an important role in leukemogenesis in myeloid malignancies [27]. MECOM rearrangements cause EVI1 overexpression, which leads to global distortion of hematopoiesis and adverse prognosis in AML. Summerer et al. [28] and Rogers et al. [21] found in a study of 120 patients that the conventional classification of patients with myeloid neoplasms carrying MECOM rearrangements into MDS or AML applying a threshold of 20% bone marrow blasts does not reflect genetic profiles or clinical outcome.
In addition to AML, NPM1 mutation has been detected in MDS (2%) and myelodysplastic/myeloproliferative neoplasms (MDS/MPN) (3%), with MDS/MPN represented by mainly chronic myelomonocytic leukemia (CMML). Blasts in NPM1 mutated cases often show monocytic differentiation (Fig. 2). One of the largest multicenter cohorts of myeloid neoplasms with mutated NPM1 and less than 20% blasts was reported by Patel et al. [29] and showed that they occurred in younger patients and were more commonly associated with a normal karyotype when compared with comparable NPM1 wild-type myeloid neoplasms. The mutation landscape was also different, as NPM1-mutated MN more commonly showed DNMT3A and PTPN11 mutations, while ASXL1, RUNX1, TP53, IDH1, IDH2, FLT3, NRAS, and KRAS mutations were less common than in the NPM1 wild-type neoplasms [21]. When looking at the clinical treatment and outcomes, most patients with NPM1-mutated MN (73%) were treated with hypomethylating agents (HMA) upfront, and 39% progressed to AML at a median time of 5.2 months. As a contrast, none of the patients treated with intensive induction chemotherapy progressed to AML. These data suggest that a more intensive chemotherapy upfront may benefit patients with NPM1-mutated myeloid neoplasms [29]. Montalban-Bravo et al. [30] reported similar observations in a smaller patient cohort of 31 patients. Based on these studies, the ICC classification has lowered the required blast for AML with mutated NPM1 to 10%, similar to the cutoff for AML with recurring cytogenetic abnormalities.
AML with in-frame bZIP CEBPA mutations
CEBPA is a single-exon gene located on chromosome 19.q13.1 that encodes for CCAAT/enhancer-binding protein-α, a lineage-specific basic leucine zipper (bZIP) transcription factor required to form myeloid progenitors from multipotent hematopoietic stem cells [31, 32]. The most common CEBPA mutations in AML are N-terminus frameshift mutations that result in premature truncation of the p42 isoform while preserving the expression of the p30 isoform. Other CEBPA mutations are usually in-frame insertions or deletions at the C-terminus basic leucine zipper region that interfere with DNA binding and dimerization [33]. CEBPA mutation is found in 7–16% of adults and 4.5–15% of pediatric AML patients. CEBPA mutations in AML have been associated with FAB M1 and M2 morphology, high CD34 expression on blasts, and predominance in the normal karyotype. A favorable prognosis was previously noted in patients with biallelic or double mutations, while patients with monoallelic CEBPA mutations (CEBPAsm) did not differ in their response to treatment from AML patients with wild-type CEBPA [34]. This finding led to the inclusion of biallelic CEBPA mutations as an independent entity in the 2016 WHO classification, as well as a favorable prognostic group in the ELN2017 recommendations. However, the impact of monoallelic CEBPA mutations has now been investigated in more detail in a few studies. In a study of 4708 adults with AML, Taube et al. [35] found that CEBPA mutations that are in-frame mutations affecting the basic leucine zipper region (bZIP) confer a favorable outcome, irrespective of their occurrence as biallelic (CEBPAbi) or single mutation (CEBPAsm). These patients present at a younger age, with higher white blood cell counts and higher frequency of GATA2 mutations, and are able to achieve high complete remission rates and long median event-free and overall survival. Their findings are in line with a recent report in 2958 pediatric AML cases also demonstrating that CEBPA bZIP domain mutations are associated with favorable clinical outcomes, regardless of mono- or biallelic mutational status [36]. Based on this data, the ICC created the category of AML with in-frame bZIP CEBPA mutations; other types of CEBPA mutations, whether monoallelic or biallelic, are not considered as a distinct disease group.
AML with mutated TP53
Alterations involving the TP53 locus are complex and include gene deletions and loss of heterozygosity as well as single nucleotide and insertion/deletion mutations [37]. Most cancer-associated TP53 mutations, including those in AML, are missense mutations that involve the DNA-binding domain (DBD) [38]. Mutant premature termination codons and frameshift mutations result in strong disruption of p53 function, whereas the impact of mutations resulting in a single amino-acid substitution or deletion is dependent on their position within the DBD. Among patients with a new diagnosis of AML, at least 10% will have disease-harboring mutations in TP53 but up to 30% in certain subpopulations such as those with secondary AML, therapy-related AML, or acute erythroid leukemia [39,40,41,42]. TP53 mutation is considered to be in the adverse prognostic group of the 2017 ELN classification [43], and recent data suggest that TP53-mutated AML confers a particularly poor prognosis compared with other ELN adverse cases, with a 2-year median overall survival of only 12.8% even when intensively treated [44]. The dismal effect of TP53 on patient outcome appears to transcend both blast count and disease ontogeny, with equally poor outcomes whether patients present as MDS or AML, and whether the disease is therapy-related or clinically de novo [45].
The clinical impact of the TP53 alteration in AML and MDS depends on whether the allelic disruption is monoallelic or biallelic, which determines the amount of functional TP53 protein present. Analyses of patients with TP53-mutated MDS demonstrated that approximately 40% of the population harbors disease with a copy-neutral loss of heterozygosity, which, based on the predicted absence of the functional TP53 protein, was significantly associated with inferior survival; conversely, patients with a monoallelic loss of TP53 behave similarly to patients with TP53 wild-type disease [46]. Some studies have suggested that higher TP53 VAF (> 40%) was also associated with shorter survival, although this has not been found in other studies of TP53-mutated AML [47, 48]. While multi-hit TP53 mutation is required for MDS with mutated TP53, in AML and MDS/AML with mutated TP53, any pathogenic TP53 mutation VAF of ≥ 10% is considered sufficient. Pure erythroid leukemia (PEL) which has a high prevalence of at least two TP53 abnormalities (both mutations and aberrant or deleted chromosome 17p) in > 90% of cases [40] is now classified as AML with mutated TP53 if it meets PEL criteria, which has remained same as was previously defined in WHO classification (1).
Diagnostic qualifiers
To reduce confusion caused by the substantial overlap of prior AML categories, the classification now identifies ontological associations as qualifiers to the diagnosis rather than as specific disease categories. All AML cases that are therapy-related should be qualified as such by entering a “therapy-related” statement after the diagnosis. Although it remains important to recognize therapy-relatedness of myeloid neoplasms, the first priority is to classify the disease according to its morphologic and genetic features. The single gene mutation or gene fusion categories will now take precedent over the myelodysplasia-related gene mutation and the myelodysplasia-related cytogenetic groups, though such findings may again impact prognosis in the genetic groups and should be noted in the diagnosis. After excluding all other genetic categories, some cases will remain unclassified and those will continue to be diagnosed as AML, NOS. Similar modifiers should be used for cases that progress from MDS and from MDS/MPN or are associated with germline predisposition (see Table 3). In the hierarchical ICC AML classification, the presence of an AML-defining recurrent genetic abnormality (as listed in Tables 1 and 2) would take the first precedent, followed by myelodysplasia-related mutations and myelodysplasia-related cytogenetic abnormalities. Both NMP1 and TP53 mutated AML are considered AML with recurrent genetic abnormalities (based on gene mutations) and, if present together, should be listed as such. If TP53 mutation is present along with myelodysplasia-related gene mutations, a diagnosis of AML with mutated TP53 should be made.
Diagnostic evaluation
A thorough patient history and relevant clinical data, including a physical examination, imaging findings, and blood laboratory values, should be obtained [49]. Cytogenetics and next-generation sequencing should be utilized to investigate the genomic features of each new patient’s AML. ELN genetic risk stratification can then be employed to assess prognosis and has been adopted by multiple society consensus guidelines including the NCCN.
Multiparameter flow cytometry (FCM) is important for lineage assignment of newly diagnosed acute leukemia. In AML, FCM is necessary to confirm acute myeloid leukemia with minimal differentiation and to detect monocytic differentiation. Characteristic findings in AML with main specific genetic abnormalities have been described and summarized in the WHO 2008 and 2016 publications [1, 50]. AML with NPM1 mutation has been at first described as APL-like due to CD34 and HLA-DR negative blast populations (1) but it has been immunophenotypically characterized in detail in more recent publications. Three subtypes of marker expression have been described: blastic, myelomonocytic, and purely monocytic [51, 52]. The presence of at least a small monocytic population and CD11c positive blast population in NPM1 + AML makes the quick FCM differentiation between APL and NMP1 + AML easy. In AML with monocytic differentiation, there is a sequence of antigen expression (including progressive acquisition of CD14, CD35, and decrease of HLA-DR on CD64-positive and CD300-negative cells) that is extremely helpful for precise identification of the stage of the maturational arrest of monocytic-lineage blast cells and promonocytes, as well as the maturation status of residual monocytic cells, whenever they are also present. Increasing reactivity for CD36, CD35, and CD14 is observed in maturing promonocytes. Fully mature monocytes are characterized by their reactivity forCD300e, at a stage where CD14 and CD35 expression have already reached their highest levels, after a slight decrease in HLA-DR expression. Therefore, the expression of CD64 by blast cells that retain HLA-DR expression, even in the absence of positivity for CD34 and CD117, allows early discrimination between monocytic-lineage AML and other AML subtypes [53].
Like AML with RUNX1::RUNX1T1, RUNX1-mutated AML has been associated with mixed phenotype acute leukemia (MPAL) features [54] and with the expansion of the plasmacytoid dendritic cell compartment [55, 56].
AML with myelodysplasia-related genetic abnormalities (both chromosomal abnormalities and gene mutations) often carry immunophenotypic features like those described in MDS [57,58,59] (Fig. 3). The simultaneous occurrence of several mutations and heterogeneous complex karyotypes makes it difficult to characterize specific patterns associated with specific mutations. However, high expression of CD34 and aberrant expression of CD7 have been associated with TP53 mutation [60]. CD14 expression in the granulocytic compartment [61] and increased CD45RA expression in the CD34 + /CD38 stem cell compartment have been described in cases with chromosome 7 abnormalities [62].
FCM immunophenotyping is also of importance to detect MPAL characteristics of blast populations. The MPAL criteria for lineage assignment are still a matter of some debate [63,64,65,66]. With the new definition of AML and MDS/AML with myelodysplasia-related genetic changes, many cases previously assigned to the MPAL category with predominant myeloid blast populations will now be diagnosed as AML based on cytogenetic or mutation findings or MDS/AML. However, one should be aware of MPAL cases with predominant lymphatic populations that may carry similar genetic abnormalities (especially in the pediatric population) [67].
While historically there has been concern that treatment delays to wait for genomic tests could harm patient outcomes, there is data to suggest this is not the case. In a study of 599 French patients (40% were aged ≥ 60 years), a delay in treatment with a median time-to-treatment of 8 days was not associated with early death, complete response (CR) rate, or OS in multivariable analysis [68]. More recently, a preliminary analysis of the Beat AML Master trial of 395 patients aged ≥ 60 years of age demonstrated the feasibility of obtaining cytogenetic and NGS testing to target induction therapy [69]. Approximately 95% of patients had these tests completed within 7 days and the median OS for patients assigned to three investigational substudies on the basis of genetic features was significantly longer than those who received standard-of-care treatment (12.8 vs. 3.9 months) [69]. Therefore, the more focused molecular approach proposed by the ICC is feasible and should allow for improved patient outcomes.
Measurable residual disease
The term “minimal residual disease” was replaced by “measurable residual disease” (MRD) in 2018 by the European Leukemia Net (ELN) AML expert panel and the new term is applied in studies by others [70, 71]. Irrespective of the methodology employed, MRD is a strong predictor of relapse and shorter survival in AML patients [71]. ELN recommendations based on a Delphi poll on both flow cytometry (FCM) and molecular MRD detection were recently updated [72]. In FCM, the application of a multiparameter approach with the integration of the diagnostic leukemia-associated immunophenotype (LAIP) and different from normal (DfN) aberrant immunophenotype approaches is recommended, ideally with a possibility to compare the follow-up sample with the diagnostic sample analyzed with the same panel. A combination of LAIP and DfN approaches makes it possible to detect both residual and new emergent leukemic clones. To reliably use flow MRD for clinical decision-making, the lower limit of detection (LLOD) and lower limit of quantification (LLOQ) should be reported for each MRD measurement [72]. Since relapses occur also in MRD-negative patients, further research is focusing on measuring the frequency and targeting of residual leukemic stem cells, which are a subpopulation of CD34 + /CD38-leukemic cells capable of self-renewal and may be resistant to therapy [73].
In molecular MRD detection, real-time quantitative polymerase chain reaction (RT-qPCR) for detection of common fusion transcripts [73] and mutations in genes such as NPM1, FLT3-ITD, CEBPA, IDH1, IDH2, KIT, RAS, RUNX1, and TP53 or WT1 gene overexpression is considered as the “gold standard” [74]. A method that is gaining increased interest is droplet digital (dd)PCR that does not require a standard curve, measures the absolute number of the molecule of interest, and can be applied to detect and quantify the level of individual somatic gene mutations [75]. ddPCR is limited by the requirement for mutation-specific primers and probes and is therefore most suitable for monitoring patients with highly recurrent mutations such as those in NPM1, IDH1, IDH2, and FLT3. The use of high-sensitivity, error-corrected next-generation sequencing (NGS) in MRD detection overcomes some limitations of ddPCR and can detect mutations in any targeted gene allowing for MRD detection in nearly all AML patients. While previously too expensive or logistically complicated to implement, these methods are now entering clinical use. NGS-based MRD methods are challenged by the inability to distinguish between leukemia-related somatic mutations and persistent clonal hematopoiesis (generally persistent mutations in DNMT3A, TET2, or ASXL1—so-called DTA mutations) as well as the necessity to consider germline mutations in genes that may be involved in leukemogenesis [72]. These challenges must be overcome before NGS-MRD can be recommended as a stand-alone MRD technique [72].
References
Arber DA, Orazi A, Hasserjian R, Thiele J, Borowitz MJ, Le Beau MM et al (2016) The 2016 revision to the World Health Organization classification of myeloid neoplasms and acute leukemia. Blood 127(20):2391–2405
Bennett JM, Catovsky D, Daniel MT, Flandrin G, Galton DA, Gralnick HR et al (1976) Proposals for the classification of the acute leukaemias French-American-British (FAB) co-operative group. Br J Haematol 33(4):451–458
Arber DA, Orazi A, Hasserjian RP (2022) International Consensus Classification of myeloid neoplasms and acute leukemia: integrating morphological, clinical, and genomic data. Blood blood 2022015850. https://doi.org/10.1182/blood.2022015850.
Vardiman J, Reichard K (2015) Acute myeloid leukemia with myelodysplasia-related changes. Am J Clin Pathol 144:29–43
Montalban-Bravo G, Kanagal-Shamanna R, Class CA, Sasaki K, Ravandi F, Cortes JE, Daver N, Takahashi K, Short NJ, DiNardo CD, Jabbour E, Borthakur G, Naqvi K, Issa GC, Konopleva M, Khoury JD, Routbort M, Pierce S, Do KA, Bueso-Ramos C, Patel K, Kantarjian H, Garcia-Manero G, Kadia TM (2020) Outcomes of acute myeloid leukemia with myelodysplasia related changes depend on diagnostic criteria and therapy. Am J Hematol 95(6):612–622
Mannelli F, Ponziani V, Bonetti MI, Bencini S, Cutini I, Gianfaldoni G, Scappini B et al (2015) Multilineage dysplasia as assessed by immunophenotype has no impact on clinical-biological features and outcome of NPM1-mutated acute myeloid leukemiaExp. Hematol 43(10):869-879 e22
Devillier R, Mansat-De Mas V, Gelsi-Boyer V, Demur C, Murati A, Corre J, Prebet J, Bertoli S, Brecqueville M, Arnoulet C et al (2015) Role of ASXL1 and TP53 mutations in the molecular classification and prognosis of acute myeloid leukemias with myelodysplasia-related changes. Oncotarget 6(10):8388–8396
Miesner M, Haferlach C, Bacher U, Weiss T, Macijewski K, Kohlmann K et al (2010) Multilineage dysplasia (MLD) in acute myeloid leukemia (AML) correlates with MDS-related cytogenetic abnormalities and a prior history of MDS or MDS/MPN but has no independent prognostic relevance: a comparison of 408 cases classified as “AML not otherwise specified” (AML-NOS) or “AML with myelodysplasia-related changes” (AML-MRC). Blood 116(15):2742–2751
Weinberg OK, Seetharam M, Ren L, Seo K, Ma L, Merker JD, Gotlib J, Zehnder JL, Arber DA (2009) Clinical characterization of acute myeloid leukemia with myelodysplasia-related changes as defined by the 2008 WHO classification system. Blood 113(9):1906–1908
Cancer Genome Atlas Research Network Ley TJ Miller C, Ding L et al (2013) Genomic and epigenomic landscapes of adult de novo acute myeloid leukemia. N Engl J Med 368(22):2059–2074
Döhner H, Estey E, Grimwade D, Amadori S et al (2017) Diagnosis and management of AML in adults: 2017 ELN recommendations from an international expert panel. Blood 129(4):424–447
Lindsley RC, Mar BG, Mazzola E, Grauman PV et al (2015) Acute myeloid leukemia ontogeny is defined by distinct somatic mutations. Blood 125:1367–1376
Papaemmanuil E, Gerstung M, Bullinger L, Gaidzik VI, Paschka P, Roberts ND et al (2016) Genomic classification and prognosis in acute myeloid leukemia. N Engl J Med 374:2209–2221
Gao Y, Jia M, Mao Y, Cai H, Jiang X, Cao X, Zhou D, Li J (2022) Distinct mutation landscapes between acute myeloid leukemia with myelodysplasia-related changes and de novo acute myeloid leukemia. Am J Clin Pathol 157(5):691–700
Baer C, Walter W, Stengel A, Hutter S, Meggendorfer M, Kern W, Haferlach C, Haferlach T (2019) Molecular classification of AML-MRC reveals a distinct profile and identifies MRC-like patients with poor overall survival. Blood 134(Supplement 1):2735
Tang JL, Hou HA, Chen CY, Liu CY, Chou WC, Tseng MS et al (2009) AML1/RUNX1 mutations in 470 adult patients with de novo acute myeloid leukemia: prognostic implication and interaction with other gene alterations. Blood 114(26):5352–5361
Mendler JH, Maharry K, Radmacher MD, Mrózek K, Becker H, Metzeler KH et al (2012) RUNX1 mutations are associated with poor outcome in younger and older patients with cytogenetically normal acute myeloid leukemia and with distinct gene and microRNA expression signatures. J Clin Oncol 30(25):3109–3111
Arber DA, Erba HP (2020) Diagnosis and treatment of patients with acute myeloid leukemia with myelodysplasia-related changes (AML-MRC). Am J Clin Pathol 154(6):731–741
Seymour JF, Döhner H, Butrym A, Wierzbowska A, Selleslag D, Jang JH, Kumar R et al (2017) Azacitidine improves clinical outcomes in older patients with acute myeloid leukaemia with myelodysplasia-related changes compared with conventional care regimens. BMC Cancer 17:852
Koenig KL, Sahasrabudhe KD, Sigmund AM, Bhatnagar B (2020) AML with myelodysplasia-related changes: development, challenges, and treatment advances. Genes (Basel) 11(8):845
Rogers HJ, Vardiman JW, Anastasi J, Raca G, Savage NM, Cherry AM, Arber DA et al (2014) Complex or monosomal karyotype and not blast percentage is associated with poor survival in acute myeloid leukemia and myelodysplastic syndrome patients with inv(3)(q21q26.2)/t(3;3)(q21;q26.2): a Bone Marrow Pathology Group study. Haematologica 99(5):821–9
Grimwade D, Hills RK, Moorman AV, Walker H, Chatters S, Goldstone AH, Wheatley K, Harrison CJ, Burnett AK (2010) National Cancer Research Institute Adult Leukaemia Working Group. Refinement of cytogenetic classification in acute myeloid leukemia: determination of prognostic significance of rare recurring chromosomal abnormalities among 5876 younger adult patients treated in the United Kingdom Medical Research Council trials. Blood 116:354–365
Weinberg OK, Ohgami RS, Ma L, Seo K, Ren L, Gotlib J, Seetharam M, Cherry A, Arber DA (2014) Acute myeloid leukemia with monosomal karyotype: morphologic, immunophenotypic, and molecular findings. Am J Clin Pathol 142:190–195
Kayser S, Zucknick M, Döhner K, Krauter J, Köhne CH, Horst HA et al (2012) Monosomal karyotype in adult acute myeloid leukemia: prognostic impact and outcome after different treatment strategies. Blood 119:551–558
Breems DA, Putten WLJV, Greef GED, Zelderen-Bhola SLV, Gerssen-Schoorl KBJ, Mellink CHM et al (2008) Monosomal karyotype in acute myeloid leukemia: a better indicator of poor prognosis than a complex karyotype. J Clin Oncol 26:4791–4797
Soupir CP, Vergilio JA, Dal Cin P, Muzikansky A, Kantarjian H, Jones D, Hasserjian RP (2007) Philadelphia chromosome-positive acute myeloid leukemia: a rare aggressive leukemia with clinicopathologic features distinct from chronic myeloid leukemia in myeloid blast crisis. Am J Clin Pathol 127:642–650
Wang HY, Rashidi HH (2016) The new clinicopathologic and molecular findings in myeloid neoplasms with inv(3)(q21q26)/t(3;3)(q21;q26.2). Arch Pathol Lab Med 140(12):1404–1410
Summerer I, Haferlach C, Meggendorfer M, Kern W, Haferlach T, Stengel A (2020) Prognosis of MECOM ( EVI1)-rearranged MDS and AML patients rather depends on accompanying molecular mutations than on blast count. Leuk Lymphoma 61(7):1756–1759
Patel SS, Ho C, Ptashkin RN, Sadigh S, Bagg A, Geyer JT et al (2019) Clinicopathologic and genetic characterization of nonacute NPM1-mutated myeloid neoplasms. Blood Adv 3:1540–1545
Montalban-Bravo G, Kanagal-Shamanna R, Sasaki K, Patel K, Ganan-Gomez I, Jabbour E et al (2019) NPM1 mutations define a specific subgroup of MDS and MDS/MPN patients with favorable outcomes with intensive chemotherapy. Blood Adv 3:922–933
Keeshan K, Santilli G, Corradini F, Perrotti D, Calabretta B (2003) Transcription activation function of C/EBPalpha is required for induction of granulocytic differentiation. Blood 102(4):1267–1275
Schmidt L, Heyes E, Grebien F (2020) Gain-of-function effects of N-terminal CEBPA mutations in acute myeloid leukemia. BioEssays 42(2):e1900178
Grossmann V, Schnittger S, Schindela S, Klein H-U, Eder C, Dugas M, Kern W, Haferlach T, Haferlach C, Kohlmann A (2011) Strategy for robust detection of insertions, deletions, and point mutations in CEBPA, a GC-rich content gene, using 454 next-generation deep-sequencing technology. J Mol Diagn 13(2):129–136
Wouters BJ, Löwenberg B, Erpelinck-Verschueren CAJ, van Wim LJ, Putten P, Valk JM, Delwel R (2009) Double CEBPA mutations, but not single CEBPA mutations, define a subgroup of acute myeloid leukemia with a distinctive gene expression profile that is uniquely associated with a favorable outcome. Blood 113(13):3088–3091
Taube F, Georgi JA, Kramer M, Stasik S, Middeke JM, Röllig C et al (2022) CEBPA mutations in 4708 patients with acute myeloid leukemia: differential impact of bZIP and TAD mutations on outcome. Blood 139(1):87–103
Tarlock K, Lamble AJ, Wang YC, Gerbing RB, Ries RE, Loken M et al (2021) CEBPA-bZip mutations are associated with favorable prognosis in de novo AML: a report from the Children’s Oncology Group. Blood 138(13):1137–1147
Kim MP, Lozano G (2018) Mutant p53 partners in crime. Cell Death Differ 25(1):161–168
Bouaoun L, Sonkin D, Ardin M (2016) Monica Hollstein 3 4, Graham Byrnes 1, Jiri Zavadil 3, Magali Olivier 3 TP53 variations in human cancers: new lessons from the IARC TP53 database and genomics data. Hum Mutat 37(9):865–876
Tazi Y, Arango-Ossa JE, Zhou Y, Bernard E, Thomas I, Gilkes A et al (2022) Unified classification and risk-stratification in acute myeloid leukemia. Nat Commun 13(1):4622
Kandoth C, McLellan MD, Vandin F, Ye K, Niu B, Lu C et al (2013) Mutational landscape and significance across 12 major cancer types. Nature 502:333–339
Marchesi V (2013) Genetics: the AML mutational landscape. Nat Rev Clin Oncol 10(6):305
Montalban-Bravo G, Benton CB, Wang SA, Ravandi F, Kadia T, Cortes J et al (2017) More than 1 TP53 abnormality is a dominant characteristic of pure erythroid leukemia. Blood 129:2584–2587
Döhner H, Estey E, Grimwade D, Amadori S, Appelbaum FR, Büchner T et al (2017) Diagnosis and management of AML in adults: 2017 ELN recommendations from an international expert panel. Blood 129(4):424–447
Welch JS (2022) TP53 and the star-crossed lovers MDS and AML. Blood 139(15):2265–2266
Ok CY, Patel KP, Garcia-Manero G, Routbort MJ, Peng J, Tang G, Goswami M, Young KH, Singh R, Medeiros LJ, Kantarjian HM, Luthra R, Wang SA (2015) TP53 mutation characteristics in therapy-related myelodysplastic syndromes and acute myeloid leukemia is similar to de novo diseases. J Hematol Oncol 8(8):45
Bernard E, Nannya Y, Hasserjian RP, Devlin SM, Tuechler H, Medina-Martinez JS et al (2020) Implications of TP53 allelic state for genome stability, clinical presentation and outcomes in myelodysplastic syndromes. Nat Med 26:1549–1556
Grob T, Al Hinai ASA, Sanders MA, Kavelaars FG, Rijken M, Gradowska PL et al (2022) Molecular characterization of mutant TP53 acute myeloid leukemia and high-risk myelodysplastic syndrome. Blood 139(15):2347–2354
Weinberg OK, Siddon A, Madanat YF, Gagan J, Arber DA, Dal Cin P et al (2022) TP53 mutation defines a unique subgroup within complex karyotype de novo and therapy-related MDS/AML. Blood Adv 6(9):2847–2853
Arber DA, Borowitz MJ, Cessna M, Etzell J, Foucar K, Hasserjian RP et al (2017) Initial diagnostic workup of acute leukemia: guideline from the College of American Pathologists and the American Society of Hematology. Arch Pathol Lab Med 141:1342–1393
Hrusák O, Porwit-MacDonald A (2002) Antigen expression patterns reflecting genotype of acute leukemias. Leukemia 16(7):1233–1258
Liu YR, Zhu HH, Ruan GR, Qin YZ, Shi HX, Lai YY, Chang Y, Wang YZ, Lu D, Hao L, Li JL, Li LD, Jiang B, Huang XJ (2013) NPM1-mutated acute myeloid leukemia of monocytic or myeloid origin exhibit distinct immunophenotypes. Leuk Res 37(7):737–741
Gupta M, Jafari K, Rajab A, Wei C, Mazur J, Tierens A, Hyjek E, Musani R, Porwit A (2021) Radar plots facilitate differential diagnosis of acute promyelocytic leukemia and NPM1+ acute myeloid leukemia by flow cytometry. Cytometry B Clin Cytom 100(4):409–420
Matarraz S, Almeida J, Flores-Montero J, Lécrevisse Q, Guerri V, López A, Bárrena S, Van Der Velden V, Te Marvelde JG, Van Dongen JJM, Orfao A (2017) Introduction to the diagnosis and classification of monocytic-lineage leukemias by flow cytometry. Cytometry B Clin Cytom 92(3):218–227
Merati G, Rossi M, Gallì A, Roncoroni E, Zibellini S, Rizzo E, Pietra D, Picone C, Rocca B, Cabrera CPT, Gelli E, Santacroce E, Arcaini L, Zappasodi P (2021) Enrichment of double RUNX1 mutations in acute leukemias of ambiguous lineage. Front Oncol 31(11):726637
Xiao W, Chan A, Waarts MR, Mishra T, Liu Y, Cai SF, Yao J, Gao Q, Bowman RL, Koche RP, Csete IS, DelGaudio NL, Derkach A, Baik J, Yanis S, Famulare CA, Patel M, Arcila ME, Stahl M, Rampal RK, Tallman MS, Zhang Y, Dogan A, Goldberg AD, Roshal M, Levine RL (2021) Plasmacytoid dendritic cell expansion defines a distinct subset of RUNX1-mutated acute myeloid leukemia. Blood 137(10):1377–1391
Porwit A, Béné MC (2021) The plasmacytoid dendritic cell CD123+ compartment in acute leukemia with or without RUNX1 mutation: high inter-patient variability disclosed by immunophenotypic unsupervised analysis and clustering. Hemato 2:572–585
Porwit A, van de Loosdrecht AA, Bettelheim P, Brodersen LE, Burbury K, Cremers E, Della Porta MG, Ireland R, Johansson U, Matarraz S, Ogata K, Orfao A, Preijers F, Psarra K, Subirá D, Valent P, van der Velden VH, Wells D, Westers TM, Kern W, Béné MC (2014) Revisiting guidelines for integration of flow cytometry results in the WHO classification of myelodysplastic syndromes-proposal from the International/European LeukemiaNet Working Group for Flow Cytometry in MDS. Leukemia 28(9):1793–1798
Weinberg OK, Hasserjian RP, Li B, Pozdnyakova O (2017) Assessment of myeloid and monocytic dysplasia by flow cytometry in de novo AML helps define an AML with myelodysplasia-related changes category. J Clin Pathol 70(2):109–115
Dannheim KC, Pozdnyakova O, Dal Cin P, Weinberg OK (2018) Immunophenotypic dysplasia and aberrant T-cell antigen expression in acute myeloid leukaemia with complex karyotype and TP53 mutations. J Clin Pathol 71(12):1051–1059
Dimitriou M, Woll PS, Mortera-Blanco T, Karimi M, Wedge DC, Doolittle H, Douagi I, Papaemmanuil E, Jacobsen SE, Hellström-Lindberg E (2016) Perturbed hematopoietic stem and progenitor cell hierarchy in myelodysplastic syndromes patients with monosomy 7 as the sole cytogenetic abnormality. Oncotarget 7(45):72685–72698
Chen X, Wood BL, Cherian S (2019) Immunophenotypic features of myeloid neoplasms associated with chromosome 7 abnormalities. Cytometry B Clin Cytom 96(4):300–309
Khoury JD, Solary E, Abla O, Akkari Y, Alaggio R, Apperley JF, Bejar R, Berti E, Busque L, Chan JKC, Chen W, Chen X, Chng WJ, Choi JK, Colmenero I, Coupland SE, Cross NCP, De Jong D, Elghetany MT, Takahashi E, Emile JF, Ferry J, Fogelstrand L, Fontenay M, Germing U, Gujral S, Haferlach T, Harrison C, Hodge JC, Hu S, Jansen JH, Kanagal-Shamanna R, Kantarjian HM, Kratz CP, Li XQ, Lim MS, Loeb K, Loghavi S, Marcogliese A, Meshinchi S, Michaels P, Naresh KN, Natkunam Y, Nejati R, Ott G, Padron E, Patel KP, Patkar N, Picarsic J, Platzbecker U, Roberts I, Schuh A, Sewell W, Siebert R, Tembhare P, Tyner J, Verstovsek S, Wang W, Wood B, Xiao W, Yeung C, Hochhaus A (2022) The 5th edition of the World Health Organization classification of haematolymphoid tumours: myeloid and histiocytic/dendritic neoplasms. Leukemia 36(7):1703–1719
Weinberg OK, Arber DA (2022) How I diagnose acute leukemia of ambiguous lineage. Am J Clin Pathol 158(1):27–34
Béné MC, Porwit A (2022) Mixed phenotype/lineage leukemia: has anything changed for 2021 on diagnosis, classification, and treatment? Curr Oncol Rep 24(8):1015–1022
Alexander TB, Orgel E (2021) Mixed phenotype acute leukemia: current approaches to diagnosis and treatment. Curr Oncol Rep 23(2):22
Alexander TB, Gu Z, Iacobucci I, Dickerson K, Choi JK, Xu B, Payne-Turner D, Yoshihara H, Loh ML, Horan J, Buldini B, Basso G, Elitzur S, de Haas V, Zwaan CM, Yeoh A, Reinhardt D, Tomizawa D, Kiyokawa N, Lammens T, De Moerloose B, Catchpoole D, Hori H, Moorman A, Moore AS, Hrusak O, Meshinchi S, Orgel E, Devidas M, Borowitz M, Wood B, Heerema NA, Carrol A, Yang YL, Smith MA, Davidsen TM, Hermida LC, Gesuwan P, Marra MA, Ma Y, Mungall AJ, Moore RA, Jones SJM, Valentine M, Janke LJ, Rubnitz JE, Pui CH, Ding L, Liu Y, Zhang J, Nichols KE, Downing JR, Cao X, Shi L, Pounds S, Newman S, Pei D, Guidry Auvil JM, Gerhard DS, Hunger SP, Inaba H, Mullighan CG (2018) The genetic basis and cell of origin of mixed phenotype acute leukaemia. Nature 562(7727):373–379
Bertoli S, Bérard E, Huguet F, Huynh A, Tavitian A, Vergez F et al (2013) Time from diagnosis to intensive chemotherapy initiation does not adversely impact the outcome of patients with acute myeloid leukemia. Blood 121(14):2618–2626
Burd A, Levine RL, Ruppert AS, Mims AS, Borate U, Stein EM (2020) Precision medicine treatment in acute myeloid leukemia using prospective genomic profiling: feasibility and preliminary efficacy of the Beat AML Master Trial. Nat Med 26(12):1852–1858. https://doi.org/10.1038/s41591-020-1089-8
Schuurhuis GJ, Heuser M, Freeman S et al (2018) Minimal/measurable residual disease in AML: a consensus document from the European LeukemiaNet MRD Working Party. Blood 131(12):1275–1291
Short NJ, Zhou S, Fu C et al (2020) Association of measurable residual disease with survival outcomes in patients with acute myeloid leukemia: a systematic review and metaanalysis. JAMA Oncol 6(12):1890–1899
Heuser M, Freeman SD, Ossenkoppele GJ, Buccisano F, Hourigan CS, Ngai LL, Tettero JM, Bachas C, Baer C, Béné MC, Bücklein V, Czyz A, Denys B, Dillon R, Feuring-Buske M, Guzman ML, Haferlach T, Han L, Herzig JK, Jorgensen JL, Kern W, Konopleva MY, Lacombe F, Libura M, Majchrzak A, Maurillo L, Ofran Y, Philippe J, Plesa A, Preudhomme C, Ravandi F, Roumier C, Subklewe M, Thol F, van de Loosdrecht AA, van der Reijden BA, Venditti A, Wierzbowska A, Valk PJM, Wood BL, Walter RB, Thiede C, Döhner K, Roboz GJ, Cloos J (2021) 2021 Update on MRD in acute myeloid leukemia: a consensus document from the European LeukemiaNet MRD Working Party. Blood 138(26):2753–2767
Khaldoyanidi SK, Hindoyan A, Stein A, Subklewe M (2022) Leukemic stem cells as a target for eliminating acute myeloid leukemia: gaps in translational research. Crit Rev Oncol Hematol 175:103710
Gabert J, Beillard E, van der Velden VH, Bi W, Grimwade D, Pallisgaard N, Barbany G, Cazzaniga G, Cayuela JM, Cavé H, Pane F, Aerts JL, De Micheli D, Thirion X, Pradel V, González M, Viehmann S, Malec M, Saglio G, van Dongen JJ (2003) Standardization and quality control studies of ‘real-time’ quantitative reverse transcriptase polymerase chain reaction of fusion gene transcripts for residual disease detection in leukemia - a Europe Against Cancer program. Leukemia 17(12):2318–2357
Pettersson L, Chen Y, George AM, Rigo R, Lazarevic V, Juliusson G, Saal LH, Ehinger M (2020) Subclonal patterns in follow-up of acute myeloid leukemia combining whole exome sequencing and ultrasensitive IBSAFE digital droplet analysis. Leuk Lymphoma 61(9):2168–2179
Galimberti S, Balducci S, Guerrini F, Del Re M, Cacciola R (2022) Digital droplet PCR in hematologic malignancies: a new useful molecular tool. Diagnostics (Basel) 12(6):1305
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Weinberg, O.K., Porwit, A., Orazi, A. et al. The International Consensus Classification of acute myeloid leukemia. Virchows Arch 482, 27–37 (2023). https://doi.org/10.1007/s00428-022-03430-4
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DOI: https://doi.org/10.1007/s00428-022-03430-4