Mixed-phenotype acute leukemia: clinical and laboratory features and outcome in 100 patients defined according to the WHO 2008 classification. Blood. 2011;117:3163-3171. [PMID: 21228332 DOI: 10.1182/blood-2010-10-314682]

Flow cytometric detection of leukemic blasts in Libyan pediatric patients with acute lymphoblastic leukemia

The diagnosis of acute lymphoblastic leukemia (ALL), which is the most common type of cancer in children, has become more accurate with the use of flow cytometry. Here, this technology was used to immunophenotype leukemic cells in peripheral blood samples from Libyan pediatric ALL patients. We recruited 152 newly diagnosed patients at Tripoli Medical Center (Tripoli, Libya) by morphological examination of blood and bone marrow. Twenty-three surface and cytoplasmic antigen markers were used to characterize B and T cells in circulating blood cells by four-color flow cytometry. Six children (3.9%) turned out to have biphenotypic acute leukemia, 88 (57.9%) had B ALL, and 58 (38.1%) had T ALL. There were 68 cases of pro-B ALL CD10-positive (44.7%), 8 cases of pro-B ALL CD10-negative (5.2%), 6 cases of pre-B ALL (3.9%), and 6 of mature-B ALL (3.9%). CD13 was the most commonly expressed myeloid antigen in ALL. We present immunophenotypic data for the first time describing ALL cases in Libya. The reported results indicate that the most common subtype was pro-B ALL, and the frequency of T-ALL subtype was higher compared to previous studies. Six cases were positive for both myeloid and B lymphoid markers. Our findings may provide the basis for future studies to correlate immunophenotypic profile and genetic characteristics with treatment response among ALL patients.

Clinicopathological differences between T-lymphoblastic leukemia/lymphoma, early T-precursor lymphoblastic leukemia/lymphoma, and mixed-phenotype acute leukemia with T lineage: an analysis of 41 adult cases

The histopathological diagnosis of T-lymphoblastic leukemia/lymphoma, NOS (T-ALL), is based on morphology and positivity for CD3 and TdT. Early T-precursor lymphoblastic leukemia/lymphoma (ETP-ALL) and mixed-phenotype acute leukemia (MPAL), T/M, and/or B rarely occur and are usually diagnosed using flow cytometry. Using only formalin-fixed paraffin-embedded tissue raises the risk of misdiagnosis due to underestimation. Immunostaining markers for T cell (CD1a, CD4, CD5, CD8), B cell (CD19, CD10, CD22, CD79a), and stem/myeloid-related cell (CD33, CD34, CD117, MPO, lysozyme) diagnosed 25 T-ALL cases (61%), 7 MPAL (17%), 6 ETP-ALL (15%), and 3 near ETP-ALL (7%), with subsequent analysis of their clinicopathological characteristics. Patients with MPAL had significantly poorer 2-year progression-free survival (14.3% vs. 60.4%, P = 0.012) and 5-year overall survival (28.6% vs. 65.9%, P = 0.011) than did those with T-ALL, whereas ETP-ALL and near ETP-ALL did not. Of the seven patients with MPAL, three were classified as T/B, two as T/M, and two as T/M/B. Because most MPALs (6/7) share the ETP-ALL phenotype, immunohistochemistry for CD19 and MPO should be performed to avoid misdiagnosing MPAL as ETP-ALL. All three patients with TdT-negative MPAL died of the disease. Four patients with MPO-positive MPAL relapsed during the early phase (1-9 months). Five patients received the ALL regimen, but two patients received acute myeloid leukemia and lymphoma regimens, respectively. In this study, MPAL exhibited a poorer prognosis compared to T-ALL, unlike ETP-ALL. Thus, immunohistochemical classification with multiple antibody panels is useful for accurate diagnosis and treatment.

A hybrid protocol CLAG-M, a possible player for the first-line therapy of patients with mixed phenotype acute leukemia. A Polish Adult Leukemia Group experience

Introduction

Mixed-phenotype acute leukemia (MPAL) is a rare disease with poor prognosis. So far, no standard approach has been established as the "know-how" of MPAL is based only on retrospective analyses performed on small groups of patients.

Materials and methods

In this study, a retrospective analysis of the outcomes of adult MPAL patients included in the PALG registry between 2005 and 2024 who received the CLAG-M hybrid protocol as induction or salvage therapy was performed.

Results

Sixteen of 98 MPAL patients received CLAG-M: eight as first-line and eight as salvage therapy. In the first line, two patients achieved partial response (PR), and six achieved complete remission (CR), of whom four successfully underwent allogeneic hematopoietic stem cell transplantation (alloHSCT). Two patients who did not undergo alloHSCT promptly relapsed. Within the whole group, the overall response rate (ORR) was 75% (n = 12/16). With the median follow-up of 13 months, six out of eight patients remain in CR, however, two of them died due to acute graft versus host disease. Out of eight patients who received CLAG-M in the second line, four patients (50%) obtained CR. AlloHSCT was conducted in seven cases, six of which were in CR. Only two patients remained in CR at the time of the last follow-up. Tolerance to treatment was good. The median times for severe neutropenia and thrombocytopenia were 22 days (range, 16-24) and 17 days (range, 12-24), respectively. Overall, grade 3-4 infections were observed in 12 cases, and all infections presented successful outcomes.

Conclusions

CLAG-M is an effective first-line salvage regimen for MPAL with an acceptable safety profile. Early achievement of CR with prompt alloHSCT allows for satisfactory disease control.

First report of familial mixed phenotype acute leukemia: shared clinical characteristics, Philadelphia translocation, and germline variants

While our understanding of the molecular basis of mixed phenotype acute leukemia (MPAL) has progressed over the decades, our knowledge is limited and the prognosis remains poor. Investigating cases of familial leukemia can provide insights into the role of genetic and environmental factors in leukemogenesis. Although familial cases and associated mutations have been identified in some leukemias, familial occurrence of MPAL has never been reported. Here, we report the first cases of MPAL in a family. A 68-year-old woman was diagnosed with MPAL and received haploidentical stem cell transplantation from her 44-year-old son. In four years, the son himself developed MPAL. Both cases exhibited similar characteristics such as biphenotypic leukemia with B/myeloid cell antigens, Philadelphia translocation (BCR-ABL1 mutation), and response to acute lymphoblastic leukemia-type chemotherapy. These similarities suggest the presence of hereditary factors contributing to the development of MPAL. Targeted sequencing identified shared germline variants in these cases; however, in silico analyses did not strongly support their pathogenicity. Intriguingly, when the son developed MPAL, the mother did not develop donor-derived leukemia and remained in remission. Our cases provide valuable insights to guide future research on familial MPAL.

Successful treatment of a B/T MPAL patient by chemo-free treatment with venetoclax, azacitidine, and blinatumomab

B/T mixed phenotype acute leukemia (MPAL), which represents only 2-3% of all MPAL cases, is classified as a high-risk leukemia subtype. Adults diagnosed with B/T MPAL have a notably low 3-year survival rate, estimated at 20-40%. The rarity and undercharacterization of B/T MPAL present substantial challenges in identifying an optimal treatment protocol. This report aims to shed light on this issue by presenting a case in which a patient with a complex karyotype was treated using a combination of venetoclax, azacitidine, and blinatumomab. This novel, chemo-free regimen resulted in the patient achieving both hematologic and molecular complete remission, with no severe organ or hematological toxicity observed. Notably, the patient continued to maintain molecular remission for 1 year following the transplantation. Based on these findings, the combination of venetoclax, azacitidine, and blinatumomab could be considered a potential therapeutic approach for B/T MPAL patients, meriting further investigation.

Clinico-hematological and immunophenotypic profile of acute leukemia of ambiguous lineage: A four year experience from a single tertiary care centre of West India

Background

: Acute leukemia of ambiguous lineage (ALAL) is a heterogeneous group of rare leukemias that lacks definite evidence of differentiation along one lineage. It includes acute undifferentiated leukemia and mixed-phenotype acute Leukaemia (MPAL).

Aims

The present study highlighted the clinicohematological and immunophenotypic profile of ALAL cases diagnosed in the tertiary care centre of western India.

Study Design

Retrospective observational study.

Methods and Materials

Patients diagnosed with acute leukemia, preferably their bone marrow aspirate samples, were collected in ethylene diamine tetra-acetic acid-vial. The immunophenotypic study was done using the Fluorescence Activated Cell Sorting (FACS) Canto Eight color flow cytometer and a broad panel of monoclonal antibodies. The patients were diagnosed for ALAL, based on the World Health Organization (WHO) 2017 classification.

Statistical Analysis Used

Descriptive statistics with categorical and continuous variables.

Results

Overall incidence of ALAL was about 2.1%, and singly MPAL and AUL were 1.8%, and 0.3%, in frequency, respectively. The age range was 4 to 57 (median age 21 years), of which 11 (57.9%) were adults and eight were children (42.1%). There was male predominance with Male: Female ratio of 5.3:1. On immunophenotyping, B/myeloid MPAL (42.1%) was the commonest among the ALAL. Translocation t(9;22) was the most common cytogenetic abnormality found mainly in B/myeloid MPAL. Two cases were of chronic myeloid leukemia in a mixed phenotypic blast crisis. Over all prognosis of ALAL was poor.

Conclusion

ALAL is overall associated with poor prognosis as both their diagnosis and treatment decisions are difficult owing to the lack of optimum treatment data and the rarity of the disease. Hence, A careful diagnosis with the help of immunophenotyping is crucial.

Favorable response of a patient with primary B/myeloid mixed phenotype acute Leukemia to CD19-CAR-T: Case report and literature review

RATIONALE

Mixed phenotype acute leukemia (MPAL) is a rare and heterogeneous type of leukemia known for its poor prognosis. The optimal treatment strategy for this condition currently lacks consensus, leaving uncertainty in its management. Nonetheless, a potential therapeutic option for patients with refractory MPAL who express target antigens is donor-derived chimeric antigen receptor T (CAR-T) cell therapy.

PATIENT CONCERNS

We recently reported a 61-year-old woman with MPAL and elucidated its diagnosis and treatment.

DIAGNOSIS

The diagnosis of MPAL was established based on the classification of World Health Organization in 2016.

INTERVENTIONS

Despite undergoing 3 different acute lymphoblastic leukemia (ALL) regimens and 1 acute myelogenous leukemia (AML) regimen, the patient did not achieve remission. Subsequently, the patient received human CD19-targeted CAR-T cell therapy.

OUTCOMES

The patient achieved a successful and complete remission after CAR-T cell therapy. Tragically, 8 months after CAR-T infusion, the patient experienced a relapse characterized by CD19-negative disease and ultimately passed away.

LESSONS

This case underscores the potential efficacy and safety of human-derived CD19 CAR-T cell therapy in treating refractory MPAL. While this particular patient outcome was unfortunate, it suggests that CAR-T cell therapy may still hold promise as a viable treatment option for MPAL patients unresponsive to other therapies. Further research in this field is warranted to determine the most effective treatment strategies for managing this challenging disease.

Acute myeloid leukemia with mixed phenotype is characterized by stemness transcriptomic signatures and limited lineage plasticity

Mixed phenotype (MP) in acute leukemias poses unique classification and management dilemmas and can be seen in entities other than de novo mixed phenotype acute leukemia (MPAL). Although WHO classification empirically recommends excluding AML with myelodysplasia related changes (AML-MRC) and therapy related AML (t-AML) with mixed phenotype (AML-MP) from MPAL, there is lack of studies investigating the clinical, genetic, and biologic features of AML-MP. We report the first cohort of AML-MRC and t-AML with MP integrating their clinical, immunophenotypic, genomic and transcriptomic features with comparison to MPAL and AML-MRC/t-AML without MP. Both AML cohorts with and without MP shared similar clinical features including adverse outcomes but were different from MPAL. The genomic landscape of AML-MP overlaps with AML without MP but differs from MPAL. AML-MP harbors more frequent RUNX1 mutations than AML without MP and MPAL. RUNX1 mutations did not impact the survival of patients with MPAL. Unsupervised hierarchal clustering based on immunophenotype identified biologically distinct clusters with phenotype/genotype correlation and outcome differences. Furthermore, transcriptomic analysis showed an enrichment for stemness signature in AML-MP and AML without MP as compared to MPAL. Lastly, MPAL but not AML-MP often switched to lymphoid only immunophenotype after treatment. Expression of transcription factors critical for lymphoid differentiation were upregulated only in MPAL, but not in AML-MP. Our study for the first time demonstrates that AML-MP clinically and biologically resembles its AML counterpart without MP and differs from MPAL, supporting the recommendation to exclude these patients from the diagnosis of MPAL. Future studies are needed to elucidate the molecular mechanism of mixed phenotype in AML.

Key points

AML-MP clinically and biologically resembles AML but differs from MPAL. AML-MP shows RUNX1 mutations, stemness signatures and limited lymphoid lineage plasticity.

Advances in Flow Cytometry for Mixed Phenotype and Ambiguous Leukemias

This review discusses recent updates in the diagnosis of acute leukemias of ambiguous lineage and emphasizes the necessary elements for proper flow cytometric evaluation of these cases. The current emphasis of the classification system is toward interpreting the marker expression in light of the intensity of lineage markers and avoiding a diagnosis of mixed phenotype acute leukemia based solely on immunophenotyping without considering underlying genetic findings. Novel entities including mixed phenotype acute leukemia with ZNF384 rearrangements and acute leukemias of ambiguous lineage with BCL11B rearrangements seem to show characteristic flow cytometric immunophenotypes discussed here.

Outcomes with high dose cytarabine and mitoxantrone induction for adults with mixed phenotype acute leukemia

The optimal induction strategy for mixed phenotype acute leukemia (MPAL) is unknown, though retrospective data has shown improved remission rates and overall survival with acute lymphoblastic leukemia (ALL)-based regimens. At Memorial Sloan Kettering Cancer Center (MSKCC), the most utilized induction regimen for MPAL is high dose cytarabine plus mitoxantrone ("ALL-2"), though outcomes with this regimen are not well described. In this study, outcomes to first-line induction chemotherapy in 24 patients at MSKCC with MPAL classified by 2016 World Health Organization criteria are reported. The overall response rate was 94 % (16 of 17) in patients receiving ALL-2, including 86 % (6 of 7) in patients with extramedullary disease. Thirteen patients who received ALL-2 induction proceeded to allogeneic hematopoietic cell transplant (allo-HCT). The most common toxicity associated with ALL-2 was febrile neutropenia, documented in 12 patients. With a median follow-up of 37 months, median overall survival was not reached in the ALL-2 cohort, and 3-year overall survival was 62 %. In multivariate analysis, age ≥ 60 years and MPAL with isolated extramedullary disease were associated with significantly worse overall survival (P = .009 and P = .01, respectively). These results support further prospective investigation of ALL-2 as a front-line induction regimen for adults with MPAL.

Transcriptomic classes of BCR-ABL1 lymphoblastic leukemia

In BCR-ABL1 lymphoblastic leukemia, treatment heterogeneity to tyrosine kinase inhibitors (TKIs), especially in the absence of kinase domain mutations in BCR-ABL1, is poorly understood. Through deep molecular profiling, we uncovered three transcriptomic subtypes of BCR-ABL1 lymphoblastic leukemia, each representing a maturation arrest at a stage of B-cell progenitor differentiation. An earlier arrest was associated with lineage promiscuity, treatment refractoriness and poor patient outcomes. A later arrest was associated with lineage fidelity, durable leukemia remissions and improved patient outcomes. Each maturation arrest was marked by specific genomic events that control different transition points in B-cell development. Interestingly, these events were absent in BCR-ABL1⁺ preleukemic stem cells isolated from patients regardless of subtype, which supports that transcriptomic phenotypes are determined downstream of the leukemia-initialing event. Overall, our data indicate that treatment response and TKI efficacy are unexpected outcomes of the differentiation stage at which this leukemia transforms.

Treatment of Relapsed B/T-cell Mixed Phenotype Acute Leukemia With Blinatumomab

Here, we describe the treatment of a patient with relapsed/refractory B/T mixed phenotype acute leukemia (MPAL) using blinatumomab monotherapy, the first bispecific T cell engager (BiTE) approved by the FDA for relapsed/refractory B cell acute lymphoblastic leukemia (B-ALL). A 64-year-old man with a history of stage 3 chronic kidney disease and type 2 diabetes mellitus was discovered to have B/T MPAL on bone marrow biopsy during hospitalization for dyspnea due to pulmonary embolism. The patient achieved brief remission with blinatumomab treatment before succumbing to neutropenic sepsis. The lack of sufficient data to guide therapy in MPAL remains a challenge, highlighting the potential of new targeted approaches such as blinatumomab to improve outcomes in relapsed/refractory MPAL.

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

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

Engineering CAR-NK cells targeting CD33 with concomitant extracellular secretion of anti-CD16 antibody revealed superior antitumor effects toward myeloid leukemia

Acute myeloid leukemia (AML) is a common form of acute leukemia, and the currently available treatments are unsatisfactory. In the present study, we report an immune cell therapeutic strategy that employed genetically modified bifunctional CAR-NK cells. These cells combined the efficient targeting of AML cells by the CD33 molecule with the concomitant stimulation of NK cell-mediated cytotoxicity via the expression and extracellular secretion of anti-CD16 antibody (B16) that binds back to the FC receptor of NK cells. Compared to CAR-NK cells that target CD33 only, the bifunctional CD33/B16 CAR-NK cells showed superior killing efficiency toward AML cells in vitro. The increase in efficiency was approximately four-fold, as determined based on the number of cells needed to achieve 80% killing activity. An in vivo study using a xenograft model also revealed the effective clearance of leukemic cells and much longer survival, with no relapse or death for at least 60 days. In addition, the safety of CAR-NK cells did not change with additional expression of B16, as determined by the release of cytokines. These data revealed the development of a promising CAR-NK approach for the treatment of patients with AML, which may improve CAR-NK-based treatment strategy in general and may potentially be used to treat other tumors as well.

Multicenter retrospective analysis of clinical outcome of adult patients with mixed-phenotype acute leukemia treated with acute myeloid leukemia-like or acute lymphoblastic leukemia-like chemotherapy and impact of allogeneic stem cell transplantation: a Campus ALL study

Mixed-phenotype acute leukemia (MPAL) is a rare disease. Treatment is often similar to that of acute lymphoblastic leukemia (ALL), but the outcome in adults and the role of allogeneic stem cell transplantation (AlloSCT) are not well defined. We report on 77 adult patients diagnosed with MPAL over the last 10 years and treated with a curative intent. Median age was 49 years; 7.6% of cases had a BCR::ABL1 rearrangement. Thirty patients (39%) were treated with an acute myeloid leukemia (AML)-like induction and 47 (61%) with an ALL-like scheme. The complete remission (CR) rate was 67.6% and an ALL-like therapy was associated with a better CR rate (P = 0.048). The median OS was 41.9 months; age ≤ 60 years was associated with a better OS (67 vs 26 months, P = 0.014). An AlloSCT was performed in 50 patients (65%). The 5-year OS of transplanted patients was 54%. The OS post-AlloSCT was better in patients who were minimal residual disease (MRD)-negative prior to transplant (75.8% vs 45.2%, P = 0.06). This study shows that MPAL patients respond better to an ALL-like induction therapy; that consolidation therapy should include, whenever possible, an AlloSCT and that MRD negativity should be a primary endpoint of treatment.

Recognizing Minor Leukemic Populations with Monocytic Features in Mixed-Phenotype Acute Leukemia by Flow Cell Sorting Followed by Cytogenetic and Molecular Studies: Report of Five Exemplary Cases

Mixed-phenotype acute leukemia (MPAL), a rare and heterogeneous category of acute leukemia, is characterized by cross-lineage antigen expression. Leukemic blasts in MPAL can be represented either by one population with multiple markers of different lineages or by several single-lineage populations. In some cases, a major blast population may coexist with a smaller population that has minor immunophenotypic abnormalities and may be missed even by an experienced pathologist. To avoid misdiagnosis, we suggest sorting doubtful populations and leukemic blasts and searching for similar genetic aberrations. Using this approach, we examined questionable monocytic populations in five patients with dominant leukemic populations of B-lymphoblastic origin. Cell populations were isolated either for fluorescence in situ hybridization or for clonality assessment by multiplex PCR or next-generation sequencing. In all cases, monocytic cells shared the same gene rearrangements with dominant leukemic populations, unequivocally confirming the same leukemic origin. This approach is able to identify implicit cases of MPAL and therefore leads to the necessary clinical management for patients.

Integrative genomic and transcriptomic profiling reveals distinct molecular subsets in adult mixed phenotype acute leukemia

Mixed phenotype acute leukemia (MPAL) is a subtype of leukemia in which lymphoid and myeloid markers are co-expressed. Knowledge regarding the genetic features of MPAL is lacking due to its rarity and heterogeneity. Here, we applied an integrated genomic and transcriptomic approach to explore the molecular characteristics of 176 adult patients with MPAL, including 86 patients with T-lymphoid/myeloid MPAL (T/My MPAL-NOS), 42 with Ph+ MPAL, 36 with B-lymphoid/myeloid MPAL (B/My MPAL-NOS), 4 with t(v;11q23), and 8 with MPAL, NOS, rare types. Genetically, T/My MPAL-NOS was similar to B/T MPAL-NOS but differed from Ph+ MPAL and B/My MPAL-NOS. T/My MPAL-NOS exhibited higher CEBPA, DNMT3A, and NOTCH1 mutations. Ph+ MPAL demonstrated higher RUNX1 mutations. B/T MPAL-NOS showed higher NOTCH1 mutations. By integrating next-generation sequencing and RNA sequencing data of 89 MPAL patients, we defined eight molecular subgroups (G1-G8) with distinct mutational and gene expression characteristics. G1 was associated with CEBPA mutations, G2 and G3 with NOTCH1 mutations, G4 with BCL11B rearrangement and FLT3 mutations, G5 and G8 with BCR::ABL1 fusion, G6 with KMT2A rearrangement/KMT2A rearrangement-like features, and G7 with ZNF384 rearrangement/ZNF384 rearrangement-like characteristics. Subsequently, we analyzed single-cell RNA sequencing data from five patients. Groups G1, G2, G3, and G4 exhibited overexpression of hematopoietic stem cell disease-like and common myeloid progenitor disease-like signatures, G5 and G6 had high expression of granulocyte-monocyte progenitor disease-like and monocyte disease-like signatures, and G7 and G8 had common lymphoid progenitor disease-like signatures. Collectively, our findings indicate that integrative genomic and transcriptomic profiling may facilitate more precise diagnosis and develop better treatment options for MPAL.

Genomic Landscape of Mixed-Phenotype Acute Leukemia

Mixed-phenotype leukemia (MPAL) is a type of acute leukemia in which the blast population shows mixed features of myeloid, T-lymphoid, and/or B-lymphoid differentiation. MPALs are rare and carry a poor prognosis, thus, often pose both a diagnostic and therapeutic challenge. Conventionally, the diagnosis of MPAL requires either a single blast population with a lineage-defining phenotypic expression of multiple lineages (myeloid, B-cell and/or T-cell) (biphenotypic) or two distinct blast populations that each independently satisfy criteria for designation as AML, B-ALL, and/or T-ALL (bilineage). Given the rarity of MPAL, minimal studies have been performed to describe the genomic landscape of these neoplasms. IRB approval was obtained. Central MCC database was searched for any patient with a diagnosis of acute undifferentiated leukemia (AUL), acute leukemia of ambiguous lineage (ALAL), and MPAL. All patient diagnoses were manually reviewed by a hematopathologist to confirm the diagnosis of MPAL. Genomic and molecular data were collated from the EMR and bioinformatically from MCC genomics repositories. Twenty-eight patients with MPAL were identified. Thirteen were female and 15 were male. Average age was 56 years old (range = 28-81). Ten cases were biclonal and 18 were biphenotypic. Diagnoses were as follows: B/myeloid (n = 18), T/myeloid (n = 9), and T/B (n = 1). Cytogenetic analysis (Karyotype +/- FISH) was available for 27 patients. The most frequent recurrent abnormalities were complex karyotype (n = 8), BCR/ABL1 translocation (n = 6), Del 5q/-5 (n = 4), Polysomy 21 (n = 4). Mutational analysis was available for 18 patients wherein mutations were detected in 45 unique genes. The most frequently mutated genes were TP53 (7), RUNX1 (6), WT1 (4), MLL2 (3), FLT3 (3), CBL (2), ASXL1 (2), TET2 (2), MAP3K6 (2), MLL (2), and MAP3K1 (2). Targetable or potentially targetable biomarkers were found in 56% of cases. Overall survival was 19.5 months (range = 0-70 m). Ten patients were treated with an allogeneic stem cell transplant and had superior outcome (p = 0.0013). In one the largest series of MPAL cases to date, we corroborate previous findings with enriched detection of RUNX1 and FLT3-ITD mutations along with discovery of unreported mutations (MAP3K) that may be amenable to therapeutic manipulation. We also report the frequent occurrence of AML with MDS-related changes (AML-MRC)-defining cytogenetic abnormalities (26%). Finally, we show that those patients that received stem cell transplant had a better overall survival. Our findings support the need to genomically profile MPAL cases to exploit opportunities for targeted therapies in this orphan disease with dismal prognosis.

Acute myeloid leukemia with myelodysplasia-related changes and blasts of the mixed T/myeloid phenotype: a case report

A rare but clinically important diagnostic dilemma arises when cases meet the criteria for both acute myeloid leukemia with myelodysplasia-related changes (AML-MRC) and mixed phenotype acute leukemia, especially those that evolve from myelodysplastic syndrome. We describe a 56-year-old male patient who presented with cytopenias and was initially diagnosed with myelodysplastic syndrome with single lineage dysplasia. Nearly 1 year later, this patient progressed to acute leukemia, and his blast cells simultaneously expressed T-lymphoid and myeloid antigens. Cytogenetic analysis showed a 20q deletion, and next-generation sequencing showed mutations of ASXL1, NRAS, PHF6, RUNX1, TP53, and PIGA. He was diagnosed with AML-MRC with blasts of the mixed T/myeloid phenotype according to the latest World Health Organization guidelines. In accordance with the treatment principles of AML-MRC, we chose an AML-like regimen for four cycles, but the patient did not achieve remission. Finally, we adhered to the treatment principles of mixed phenotype acute leukemia, and he achieved remission after a course of ALL-like regimen chemotherapy.

Mixed-Phenotype Acute Leukemia: Clinical Diagnosis and Therapeutic Strategies

Mixed-phenotype acute leukemia (MPAL) comprises a heterogenous group of leukemias that are genetically, immunophenotypically, and clinically, diverse. Given the rarity of the disease, the diagnosis and treatment of MPAL is extremely challenging. Recent collaborative efforts have made significant progress in understanding the complex genomic landscape of MPAL. Some retrospective studies support starting ALL-type induction followed by an allogeneic stem cell transplant(allo-sct) in the first complete remission; however, due to the inherent bias of retrospective data and small case series, a prospective validation of AML- and ALL-based regimen, and the incorporation of targeted therapies based on genetics and immunophenotype are warranted. The prognosis of adults and children with MPAL varies; this justifies modulating the intensity of therapy, including the use of allo-sct as a consolidation strategy.

Highly precise breakpoint detection of chromosome balanced translocation in chronic myelogenous leukaemia: Case series

Chronic myelogenous leukaemia (CML) has a special phenomenon of chromosome translocation, which is called Philadelphia chromosome translocation. However, the detailed connection of this structure is troublesome and expensive to be identified. Low‐coverage whole genome sequencing (LCWGS) could not only detect the previously unknown chromosomal translocation, but also provide the breakpoint candidate small region (with an accuracy of ±200 bases). Importantly, the sequencing cost of LCWGS is about US$300. Then, with the Sanger DNA sequencing, the precise breakpoint can be determined at a single base level. In our project, with LCWGS, BCR and ABL1 are successfully identified to be disrupted in three CML patients (at chr22:23,632,356 and chr9:133,590,450; chr22:23,633,748 and chr9:133,635,781; chr22: 23,631,831 and chr9:133,598,513, respectively). Due to the reconnection after chromosome breakage, classical fusion gene (BCR::ABL1) was found in bone marrow and peripheral blood. The precise breakpoints were helpful to investigate the pathogenic mechanism of CML and could better guide the classification of CML subtypes. This LCWGS method is universal and can be used to detect all diseases related to chromosome variation, such as solid tumours, liquid tumours and birth defects.

Characteristics, Treatment Complexity, and Outcome of Mixed-Phenotype Acute Leukemia in Children in a Low–Middle-Income Country

Background

Mixed-phenotype acute leukemia (MPAL) in children is an uncommon subtype of acute leukemia that cannot be definitively assigned to a specific lineage. There is no consensus on the best approach to therapy. Management is more complex in low–middle-income countries (LMICs).

Aim

To evaluate the clinicopathological characteristics and outcomes of patients with MPAL in a developing country.

Patients and Methods

A retrospective descriptive study of 42 pediatric patients newly diagnosed with MPAL from July 2007 until December 2017.

Results

The immunophenotyping was T/Myeloid in 24 patients (57.1%) and B/Myeloid in 16 (38.1%). Three subjects had MLL gene rearrangement, two had Philadelphia-positive chromosomes, and eight had FMS-like tyrosine kinase 3 (FLT3-ITD) internal tandem duplication (FLT3-ITD) with a ratio >0.4. Two subjects died before starting chemotherapy. Ten patients (25%) received acute lymphoblastic leukemia (ALL) induction, and all achieved complete remission (CR) with no induction deaths and no shift of therapy. Thirty patients (75%) started therapy with acute myeloid leukemia (AML) induction: five (16.6%) died during induction, 17 (56.7%) achieved CR, and 10 patients received maintenance ALL therapy after ending AML treatment. Four of the eight patients with induction failure were switched to ALL therapy. The 5-year event-free survival (EFS) and overall survival (OS) rates were 56.7% [standard error (SE): 8.1%] and 61% (SE: 8%), while the cumulative incidence of relapse was 21.7% (SE: 6.7%), with a median follow-up duration of 5.8 years. Patients treated with ALL-directed therapy had a 5-year EFS rate of 111 70% (SE: 14%) and OS rate of 78.8% (SE: 13%). Patients treated with ALL-directed therapy had a 5-year EFS rate of 70% (SE: 14.5%) and OS rate of 78.8% (SE: 13%). FLT3-ITD mutation showed a significantly lower 5-year EFS rate of 28.6% (SE: 17%) vs. 75% (SE: 9%) for the wild type, p = 0.032. Undernourished patients with a body mass index (BMI) z-score ≤-2 at presentation had a significantly lower 5-year EFS rate of 20% (SE: 17%) compared to 61.8% (SE: 8%) for patients with BMI z-score >-2, p = 0.015.

Conclusion

This study supports ALL-directed therapy for pediatric MPAL in a setting of LMIC. Given the poor outcome of FLT3-ITD, the role of FLT3 inhibitor needs to be explored in this subset of cases.

Loss of SIRT1 inhibits hematopoietic stem cell aging and age-dependent mixed phenotype acute leukemia

Aging of hematopoietic stem cells (HSCs) is linked to various blood disorders and malignancies. SIRT1 has been implicated in healthy aging, but its role in HSC aging is poorly understood. Surprisingly, we found that Sirt1 knockout improved the maintenance of quiescence of aging HSCs and their functionality as well as mouse survival in serial bone marrow transplantation (BMT) recipients. The majority of secondary and tertiary BMT recipients of aging wild type donor cells developed B/myeloid mixed phenotype acute leukemia (MPAL), which was markedly inhibited by Sirt1 knockout. SIRT1 inhibition also reduced the growth and survival of human B/myeloid MPAL cells. Sirt1 knockout suppressed global gene activation in old HSCs, prominently the genes regulating protein synthesis and oxidative metabolism, which may involve multiple downstream transcriptional factors. Our results demonstrate an unexpected role of SIRT1 in promoting HSC aging and age-dependent MPAL and suggest SIRT1 may be a new therapeutic target for modulating functions of aging HSCs and treatment of MPAL.

Mixed Phenotype/Lineage Leukemia: Has Anything Changed for 2021 on Diagnosis, Classification, and Treatment?

Purpose of Review

Recent advances in the small field of the rare mixed phenotype acute leukemias (MPAL) are presented focusing on a better understanding of their pathophysiology and search for better therapeutic approaches.

Recent Findings

Three aspects of respective classification, therapy, and immunophenotype of MPAL are reviewed. New proposals have been made to segregate MPAL subtypes based on their genomic landscape. In parallel, it was found that a large array of therapeutic approaches has been tested in the past few years with increasingly good results. Finally, we explored the use of unsupervised flow cytometry analysis to dissect subtle variations in markers expression to better characterize the variegating aspect of MPALs.

Summary

Genomic and immunophenotypic aspects more clearly link MPAL subtypes with bona fide acute myeloblastic of lymphoblastic leukemias. This is likely to impact therapeutic strategies, towards a better management and outcome.

Chronic Myelogenous Leukemia with Double Philadelphia Chromosome and Coexpression of p210 and p190 Fusion Transcripts

The Philadelphia (Ph+) chromosome, t(9;22)(q34;q11.2), originates from a chimeric gene called BCR-ABL and is present in more than 90% of CML patients. Most patients with CML express the protein p210 BCR-ABL and, with a frequency lower than 5%, express rare isoforms, the main one being p190. In the transition from the chronic phase to the blast phase (BP), additional chromosomal abnormalities, such as the presence of the double Ph+ chromosome, are revealed. Of the 1132 patients analyzed via molecular biology in this study, two patients (0.17%) showed the co-expression of the p210 and p190 isoforms for the BCR-ABL transcript, with the concomitant presence of a double Ph+ chromosome, which was observed via conventional cytogenetics and confirmed by fluorescent in situ hybridization. The BCR-ABL/ABL% p210 and p190 ratio increased in these two patients from diagnosis to progression to blast crisis. To our knowledge, this is the first report in the literature of patients who co-expressed the two main BCR-ABL transcript isoforms and concomitantly presented Ph+ chromosome duplication. The evolution from the chronic phase to BP often occurs within 5 to 7 years, and, in this study, the evolution to BP was earlier, since disease-free survival was on average 4.5 months and overall survival was on average 9.5 months. The presence of the p190 transcript and the double Ph+ chromosome in CML may be related to the vertiginous progression of the disease.

Transcriptome analysis reveals SALL4 as a prognostic key gene in gastric adenocarcinoma

BACKGROUND

Stomach adenocarcinoma (STAD) dominates 80-90% of gastric cancer (GC). Over the years, it has been realized that the identification of the genes responsible for gastric carcinogenesis is essential to understand the biomarker discovery.

METHODS

This study aims to identify candidate genes for biomarker discovery in STAD. RNA-Seq was performed on three paired tumor-normal and one unpaired tumor samples from four GC patients and investigated for differentially expressed genes (DEGs) using DESeq2. Gene set enrichment analysis were performed. The DEGs were compared with two STAD microarray datasets available on Gene Expression Omnibus (GEO) database. Survival study (OS) were performed using KM-Plotter on the common genes between all the datasets.

RESULTS

Totally, 148 DEGs were identified, wherein 55 genes were upregulated and 93 genes were downregulated with |log2foldchange| > 1 and Benjamini-Hochberg (BH) Adjusted P value < 0.01. Cell adhesion molecule (CAM) Pathway was found to be the most significant among the upregulated genes. Gastric acid secretion and mineral absorption pathways were the most significant pathways among the downregulated genes. Comparison with two GEO datasets followed by OS analysis revealed two upregulating genes, APOC1 and SALL4 with prognostic significance.

CONCLUSION

Upregulation of APOC1 is associated with marginal overall survival (OS) and SALL4 over-expression was associated with the poor OS using KM-Plotter during 5 years data period. Our study suggests that SALL4 could be a promising biomarker candidate in STAD.

ZNF384 fusion oncoproteins drive lineage aberrancy in acute leukemia

ZNF384-rearranged fusion oncoproteins (FO) define a subset of lineage ambiguous leukemias, but their mechanistic role in leukemogenesis and lineage ambiguity is poorly understood. Using viral expression in mouse and human hematopoietic stem and progenitor cells (HSPCs) and a Ep300::Znf384 knockin mouse model, we show that ZNF384 FO promote hematopoietic expansion, myeloid lineage skewing, and self-renewal. In mouse HSPCs, concomitant lesions, such as NRASG12D, were required for fully penetrant leukemia, whereas in human HSPCs expression of ZNF384 FO drove B/myeloid leukemia, with sensitivity of a ZNF384-rearranged xenograft to FLT3 inhibition in vivo. Mechanistically, ZNF384 FO occupy a subset of predominantly intragenic/enhancer regions with increased histone 3 lysine acetylation and deregulate expression of hematopoietic stem cell transcription factors. These data define a paradigm for FO-driven lineage ambiguous leukemia, in which expression in HSPCs results in deregulation of lineage-specific genes and hematopoietic skewing, progressing to full leukemia in the context of proliferative stress.

Hypocellular Philadelphia chromosome-positive mixed-phenotype acute leukemia successfully treated with dasatinib: A case report

Both hypocellular leukemia and Philadelphia (Ph) chromosome-positive mixed-phenotype acute leukemia (MPAL) are rare subtypes of leukemia showing unfavorable outcomes and lacking established optimal management. Ph-positive leukemia most often presents with hypercellularity and hypoplasia is a rare condition. The present study reports an extremely rare case of hypocellular biclonal Ph-positive MPAL, which was diagnosed by biopsy and genetic analysis of bone marrow, and successfully treated with dasatinib and steroids. Briefly, a 77-year-old man presented with pancytopenia and flow cytometry of bone marrow could not be evaluated due to hypocellularity. The patient was finally diagnosed with hypocellular Ph-positive MPAL by genetic analysis and immunostaining of bone marrow biopsy. Although blood cells recovered with methylprednisolone pulse administration alone for concurrent optic neuritis, hematopoietic function rapidly normalized with dasatinib administered after definitive diagnosis of Ph-positive leukemia. Dasatinib and oral prednisolone were continued following methylprednisolone pulse administration and the patient achieved molecular complete remission (CR) on day 140 of treatment; molecular CR was maintained thereafter without any severe adverse events. In conclusion, the combination of dasatinib and a steroid may be one of the tolerable treatment options for elderly patients with hypocellular biclonal Ph-positive MPAL. Furthermore, genetic analysis and immunostaining of bone marrow biopsy can help with the diagnosis of leukemia with hypocellular bone marrow.

AML with BCR-ABL1 Fusion treated with Imatinib, a Hypomethylating Agent and Venetoclax

A patient with history of myelodysplastic syndrome (MDS) presented with multifocal pneumonia and was found to have Philadelphia chromosomepositive (Ph+) acute myeloid leukemia (AML). A tyrosine kinase inhibitor (TKI) was added to decitabine and venetoclax combination, providing a molecular and cytogenetic complete response despite additional cytogenetic and molecular abnormalities. She remains in remission after eleven cycles of treatment. Our report describes the tolerability and success of a triplet regimen that incorporates a TKI to a backbone of decitabine and venetoclax in a patient with high-risk disease and with significant comorbidities.

B/T mixed phenotype acute leukemia with high hyperdiploidy and lineage switch to B-cell acute leukemia

Acute leukemias are often of myeloid or lymphoid origin. However, some acute leukemias revealed an undefined differentiation into a single lineage. Mixed phenotype acute leukemia (MPAL) is an uncommon diagnosis were blasts can share B/T/myeloid phenotype. Here, we report a rare case of a 17-year-old Moroccan female diagnosed with B/T mixed phenotype acute leukemia and a high hyperdiploid karyotype who relapsed after one year of complete remission with a lineage switch to B-cell acute lymphoblastic leukemia. This case report corroborates the disclosed findings about the high occurence of abnormal karyotypes and poor prognosis of MPAL.

The association of complex genetic background with the prognosis of acute leukemia with ambiguous lineage

Acute leukemia with ambiguous lineage (ALAL) is a rare and highly aggressive malignancy with limited molecular characterization and therapeutic recommendations. In this study, we retrospectively analyzed 1635 acute leukemia cases in our center from January 2012 to June 2018. The diagnose of ALAL was based on either EGIL or 2016 WHO criteria, a total of 39 patients were included. Four patients diagnosed as acute undifferentiated leukemia (AUL) by both classification systems. Among the patients underwent high-throughput sequencing, 89.5% were detected at least one mutation and the median number of gene mutation was 3 (0–8) per sample. The most frequently mutated genes were NRAS (4, 21%), CEBPA (4, 21%), JAK3 (3, 16%), RUNX1 (3, 16%). The mutations detected in mixed-phenotype acute leukemia (MPAL) enriched in genes related to genomic stability and transcriptional regulation; while AUL cases frequently mutated in genes involved in signaling pathway. The survival analysis strongly suggested that mutation burden may play important roles to predict the clinical outcomes of ALAL. In addition, the patients excluded by WHO criteria had even worse clinical outcome than those included. The association of the genetic complexity of blast cells with the clinical outcomes and rationality of the diagnostic criteria of WHO system need to be evaluated by more large-scale prospective clinical studies.

Redefining the biological basis of lineage-ambiguous leukemia through genomics: BCL11B deregulation in acute leukemias of ambiguous lineage

Acute leukemias of ambiguous lineage (ALAL), including mixed phenotype acute leukemia (MPAL) and related entities such as early T-cell precursor acute leukemia (ETP-ALL), remain diagnostic and clinical challenges due to limited understanding of pathogenesis, reliance of immunophenotyping to classify disease, and the lack of a rational approach to guide selection of appropriate therapy. Recent studies utilizing genomic sequencing and complementary approaches have provided key insights that are changing the way in which such leukemias are classified, and potentially, treated. Several recurrent genomic alterations define leukemias that straddle immunophenotypic entities, such as ZNF384-rearranged childhood B-ALL and B/myeloid MPAL, and BCL11B-rearranged T/myeloid MPAL, ETP-ALL and AML. In contrast, some cases of MPAL represent canonical ALL/AML entities exhibiting lineage aberrancy. For many cases of ALAL, experimental approaches indicate lineage aberrancy arises from acquisition of a founding genetic alteration into a hematopoietic stem or progenitor cell. Determination of optimal therapeutic approach requires genomic characterization of uniformly treated ALAL patients in prospective studies, but several approaches, including kinase inhibitors and BH3 mimetics may be efficacious in subsets of ALAL.

Pediatric Mixed-Phenotype Acute Leukemia: What's New?

Simple Summary

Pediatric mixed-phenotype leukemia is a rare form of blood cancer in children. In this review, we cover both the evolution of treatment over the past several years and outline new emerging concepts in this disease.

Abstract

Mixed-phenotype acute leukemias (MPAL) are rare in children and often lack consensus on optimal management. This review examines the current controversies and emerging paradigms in the management of pediatric MPAL. We examine risk stratification, outcomes of recent retrospective and prospective collaborative trials, and the role of transplantation and precision genomics, and outline emerging targets and concepts in this rare entity.

CD16xCD33 Bispecific Killer Cell Engager (BiKE) as potential immunotherapeutic in pediatric patients with AML and biphenotypic ALL

Similar to pediatric acute myeloid leukemia (AML) the subgroup of biphenotypic acute lymphoblastic leukemia (ALL) is a rare complex entity with adverse outcome, characterized by the surface expression of CD33. Despite novel and promising anti-CD19 targeted immunotherapies such as chimeric antigen receptor T cells and bispecific anti-CD19/CD3 antibodies, relapse and resistance remain a major challenge in about 30% to 60% of patients. To investigate the potential role of the fully humanized bispecific antibody CD16 × CD33 (BiKE) in children with CD33⁺ acute leukemia, we tested whether the reagent was able to boost NK cell effector functions against CD33⁺ AML and biphenotypic ALL blasts. Stimulation of primary NK cells from healthy volunteers with 16 × 33 BiKE led to increased cytotoxicity, degranulation and cytokine production against CD33⁺ cell lines. Moreover, BiKE treatment significantly increased degranulation, IFN-γ and TNF-α production against primary ALL and AML targets. Importantly, also NK cells from leukemic patients profited from restoration of effector functions by BiKE treatment, albeit to a lesser extent than NK cells from healthy donors. In particular, those patients with low perforin and granzyme expression showed compromised cytotoxic function even in the presence of BiKE. In patients with intrinsic NK cell deficiency, combination therapy of CD16xCD33 BiKE and allogeneic NK cells might thus be a promising therapeutic approach. Taken together, CD16xCD33 BiKE successfully increased NK cell effector functions against pediatric AML and biphenotypic ALL blasts and constitutes a promising new option for supporting maintenance therapy or “bridging” consolidation chemotherapy before hematopoietic stem cell transplantation.

A Recurrent Cryptic MED14-HOXA9 Rearrangement in an Adult Patient With Mixed-Phenotype Acute Leukemia, T/myeloid, NOS

To define the fusion genes in T/myeloid mixed-phenotype acute leukemia (T/M MPAL), we performed transcriptome sequencing of diagnostic bone marrow samples from 20 adult patients. Our analysis identified a second instance of a recurrent MED14-HOXA9 chimeric gene resulting from the in-frame fusion of exon 23 of MED14 and exon 1 of HOXA9, the first in an adult patient. The MED14-HOXA9 fusion gene was detected in both the diagnostic and relapsed blasts with reverse transcription-polymerase chain reaction and Sanger sequencing. The patient received combined conventional chemotherapy but suffered relapse at 11 months and died of disease progression one year after the initial diagnosis. Our data suggest that MED14-HOXA9 is a cryptic recurrent aberration in T/M MPAL, which might indicate an aggressive clinical course and inferior outcome after conventional chemotherapy. Further studies will be carried out to reveal the effects of the MED14-HOXA9 fusion on the differentiation and proliferation of leukemia stem cells, as well as suitable treatment strategies for this emerging entity.

Update on Acute Leukemias of Ambiguous Lineage

Acute leukemias of ambiguous lineage are a heterogenous group of diseases that include acute undifferentiated leukemias and mixed-phenotype acute leukemias (MPALs). These leukemias pose a challenge for pathologists and clinicians alike in diagnosis, treatment, and further management. Recent genetic characterization has provided insights into their underlying biology and classification, and has offered potential for targeted therapies. This article addresses diagnosis of MPALs with examples of the most common pitfalls, recent comprehensive molecular studies, and advancement in treatment and follow-up modalities.

Aberrant expression of multiple T cell markers on diffuse large B cell lymphoma: a case report

BACKGROUND

Aberrant T cell antigen expression has been well documented in diffuse large B cell lymphomas. However, co-expression of multiple T cell antigens including CD3, which has been considered a specific marker for T cells is extremely rare. Awareness about such aberrant expression is important so as not to misdiagnose or wrongly classify a lymphoma. The aim of this article is to report such a case.

CASE PRESENTATION

A 68-year-old postmenopausal lady, diabetic and hypertensive, presented with an axillary lump of one week's duration. There was no other relevant medical history. Ultrasonography revealed multiple hypoechoic cystic lesions varying in size from 3.9 to 4.2 cm³. Aspiration was suggestive of an infective pathology. Excision biopsy of the mass was diagnosed as diffuse large B cell lymphoma with aberrant T cell antigen expression. She received 4 cycles of chemotherapy after which she was lost to follow-up.

CONCLUSION

The case presented as a diagnostic dilemma for the pathologist. The predicament lies in classifying it as a B cell lymphoma with an aberrant expression of T cell markers versus a T cell lymphoma with an aberrant B cell marker expression which has a significant implication on the treatment offered. This can be solved by looking at the expression of the B cell specific transcription factors. The key to diagnosis lies in the knowledge of their existence and the application of a panel of markers.

Immature acute leukaemias: lessons from the haematopoietic roadmap

It is essential to relate the biology of acute leukaemia to normal blood cell development. In this review, we discuss how modern models of haematopoiesis might inform approaches to diagnosis and management of immature leukaemias, with a specific focus on T-lymphoid and myeloid cases. In particular, we consider whether next-generation analytical tools could provide new perspectives that could improve our understanding of immature blood cancer biology.

Diagnosis and treatment of mixed phenotype (T-myeloid/lymphoid) acute leukemia with novel ETV6-FGFR2 rearrangement

Myeloid/lymphoid neoplasms with eosinophilia are driven by aberrant tyrosine kinases in pluripotent cells and display variable phenotypes. FGFR-driven hematolymphoid neoplasms are targetable by TKI inhibitors such as ponatinib; studies of specific FGFR inhibitors are ongoing.

Outcomes of pediatric mixed phenotype acute leukemia treated with lymphoid directed therapy: Analysis of an institutional series from India

There is limited data regarding pediatric mixed phenotype acute leukemia (MPAL) and there is no global consensus on its management yet. In this retrospective study, we analyzed the outcomes of children diagnosed with MPAL at our institute. This study included children ≤ 14 years with MPAL who presented to a tertiary cancer center in India from January 1st 2009 to December 31st 2015. Over a seven-year period, 1390 patients with leukemia presented to our institute of which 22 patients (1.5%) had MPAL. Sixteen patients (72.7%) had B/myeloid leukemia, while 4 (18.1%) and 2 (9%) patients had T/myeloid and B/T leukemia respectively. Twenty-one patients were treated with a modified BFM ALL 95 protocol. 76.1% (n = 16) of patients had a good prednisolone response (GPR) on day 8 and end-of-induction (EOI) marrow was in remission in 90.5% (n = 19). A poor prednisolone response (PPR) on day 8 correlated with an inferior relapse-free survival (25% vs 79.5%, P=.025). The 4-year event-free survival (EFS) and overall survival (OS) for the entire group was 60.8% and 64.9% respectively while the EFS for patients who had a GPR and remission at the EOI (n = 15) was 80% as compared to 16.7% in patients with PPR or induction failure. Lymphoid directed chemotherapy is seen to have good survival outcomes in pediatric MPAL. However, a PPR on day 8 or a positive EOI marrow may be an indication for more aggressive treatment.

Mixed Phenotype Acute Leukemia, B/Myeloid (Bilineal and Biphenotypic), With t(2;22)(q35;q12);EWSR1-FEV

BACKGROUND

Ewing sarcoma breakpoint region 1 gene (EWSR1) rearrangements are largely associated with the Ewing sarcoma family of tumors.

OBSERVATIONS

We report the first case of infantile, mixed phenotype acute leukemia, B/myeloid (bilineal and biphenotypic [B-lymphoid and B-lymphoid/myeloid]), with a t(2;22)(q35;q12). The EWSR1-fifth Ewing variant gene fusion and nonsense mutation in STAG2 were detected by next-generation sequencing and markedly high expression of fifth Ewing sarcoma variant mRNA detected by quantitative reverse transcription polymerase chain reaction. The patient was treated with a combined myeloid/lymphoid leukemia regimen followed by allogeneic stem cell transplant and was in complete remission at 3.8-year follow-up.

CONCLUSIONS

Our case study underscores the importance of a comprehensive evaluation of acute leukemia and provides insights into the phenotype of EWSR1 rearranged neoplasms in the context of partner genes and cell type.

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.

Early T-Cell Precursor Acute Lymphoblastic Leukemia and T/Myeloid Mixed Phenotype Acute Leukemia Possess Overlapping Characteristics and Both Benefit From CAG-Like Regimens and Allogeneic Hematopoietic Stem Cell Transplantation

Early T-cell precursor acute lymphoblastic leukemia (ETP-ALL) and T-lymphoid/myeloid mixed phenotype acute leukemia (T/M-MPAL) are closely related entities and remain a therapeutic challenge. In this study, we characterized the clinical features of 43 ETP-ALL and 41 T/M-MPAL patients and compared clinical outcomes and safety between cytarabine, aclarubicin, and granulocyte colony-stimulating factor (CAG)-like regimens in 34 patients and conventional ALL regimens in 50 patients. In our series, ETP-ALL and T/M-MPAL showed similar biological characteristics, immunophenotypes, genomic alterations, and outcomes. The complete remission (CR) rate and minimal residual disease (MRD)-negative CR rate of CAG-like regimens were significantly higher compared with conventional ALL regimens (CAG-like: 80.0% and 59.7%, respectively; P = .039; ALL: 51.4% and 31.3%, respectively; P = .048). Overall, 90.0% of cases (18/20) achieved CR using combined decitabine and CAG-like regimens. Additionally, CAG-like regimens had lower rates of grade 3 or 4 infection (18.8% vs. 38.2%; P = .059) and grade 1 or 2 hepatotoxicity (37.5% vs. 60.0%; P = .043) than conventional ALL regimens. The 38 patients who underwent allogeneic hematopoietic stem cell transplantation (allo-HSCT) in the first CR (CR1) had better overall survival (OS) and leukemia-free survival (LFS) than the 11 patients who underwent allo-HSCT in the second CR (CR2) or in no remission (median OS not reached vs. 7.6 months, P = .0004; median LFS not reached vs. 11.6 months, P = .0008). There was a significant difference in 3-year OS (95.7% vs. 52.5%; P = .0039) and LFS (95.8% vs. 43.5%; P = .0003) after allo-HSCT between pre-transplant MRD-negative and MRD-positive patients. The median OS for patients without allo-HSCT was 32.1 months in the CAG-like group compared with 12.1 months in the non-CAG-like group (P = .019). These findings suggest that ETP-ALL and T/M-MPAL possess overlapping characteristics and CAG-like regimens improve their clinical outcomes.

Hybrid chemotherapy regimen (FLAG-IDA-vincristine-prednisone) for acute leukemia with mixed-phenotype blasts

BACKGROUND

Acute leukemia with mixed-phenotype blasts is associated with poor outcomes. There are no standard treatment regimens. Due to disease heterogeneity, controversy exists over whether an AML-based, ALL-based, or a combined (hybrid) AML/ALL-based regimen is most appropriate.

MATERIALS AND METHODS

We conducted a single-center, retrospective case series review of patients with acute leukemia with mixed phenotype blasts as described by the European Group for Immunological Characterization of Leukemia (EGIL) or the 2008 WHO classification. Patients were treated from November 2014 and December 2019 with the combination chemotherapy regimen FLAG-idarubicin-vincristine-prednisone with or without rituximab. Outcomes included induction response, time to transplant, time to relapse, overall survival, time to neutrophil or platelet recovery, infection, and duration of hospitalization.

RESULTS

The median age was 68 years (range 21-77). Six patients (87.5 %) had unfavorable/complex cytogenetics. All patients achieved a complete remission (CR) or complete remission with incomplete hematologic recovery (CRi). Estimated 1-year overall survival was 85.7 %. There were no deaths during induction, with a 22 day median duration of hospitalization for induction.

CONCLUSION

The combination of FLAG, idarubicin, vincristine, and prednisone (FLAG-VIPR) demonstrated favorable induction responses in a disease state with historically poor outcomes and should be studied in a prospective clinical trial.