Clinical and laboratory features associated with myeloperoxidase expression in pediatric B‐lymphoblastic leukemia

Bone marrow-restricted aberrant myeloperoxidase expression in B-acute lymphoblastic leukemia: A diagnostic dilemma and mimicry of mixed phenotype acute leukemia

Myeloperoxidase (MPO) is the most specific marker of the myeloid lineage, essential for diagnosing acute myeloid leukemia and mixed phenotype acute leukemia with myeloid components. In this regard, we present a unique case of B-acute lymphoblastic leukemia (B-ALL) with isolated MPO expression in bone marrow blasts detected by flow cytometry and immunohistochemistry, while peripheral blood blasts were negative for MPO expression. In this report, our discussion encompasses diagnostic pitfalls from a laboratory testing perspective in similar cases and includes a literature review. Furthermore, we emphasize the necessity of conducting a comprehensive analysis for the accurate diagnosis of MPO-positive B-ALL cases.

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.

Pediatric Hematopathology in the Era of Advanced Molecular Diagnostics: What We Know and How We Can Apply the Updated Classifications

Pediatric hematologic malignancies often show genetic features distinct from their adult counterparts, which reflect the differences in their pathogenesis. Advances in the molecular diagnostics including the widespread use of next-generation sequencing technology have revolutionized the diagnostic workup for hematologic disorders and led to the identification of new disease subgroups as well as prognostic information that impacts the clinical treatment. The increasing recognition of the importance of germline predisposition in various hematologic malignancies also shapes the disease models and management. Although germline predisposition variants can occur in patients with myelodysplastic syndrome/neoplasm (MDS) of all ages, the frequency is highest in the pediatric patient population. Therefore, evaluation for germline predisposition in the pediatric group can have significant clinical impact. This review discusses the recent advances in juvenile myelomonocytic leukemia, pediatric acute myeloid leukemia, B-lymphoblastic leukemia/lymphoma, and pediatric MDS. This review also includes a brief discussion of the updated classifications from the International Consensus Classification (ICC) and the 5th edition World Health Organization (WHO) classification regarding these disease entities.

Adult mixed phenotype acute leukemia (MPAL): B/myeloid MPALisoMPO is distinct from other MPAL subtypes

INTRODUCTION

Myeloperoxidase (MPO) is considered a specific marker of myeloid/non-monocytic lineage in the diagnosis of mixed phenotype acute leukemia (MPAL). However, the clinical significance of isolated dim MPO expression in otherwise typical B lymphoblastic leukemia (B-ALL; referred to as B/myeloid MPAL^isoMPO ) in adult patients is unknown.

METHODS

We compared flow cytometric immunophenotype and clinicopathological findings among cases of B/myeloid MPAL^isoMPO (n = 13), other MPAL subtypes (n = 10, B/myeloid and T/myeloid MPAL), B-ALL (n = 64), and acute myeloid leukemia (AML, n = 58), using the 2016 WHO classification. For MPAL cases, MPO was reported as the percent of MPO positive blasts and its intensity (dim or moderate/strong). The pattern of heterogenous antigen expression (inversely coordinated expression between myeloid and lymphoid markers and cell size) was assessed.

RESULTS

Cases of B/myeloid MPAL^isoMPO showed a fairly homogenous single B-lineage blast population with dim MPO expression whereas cases of other MPAL subtypes displayed heterogeneous antigen expression and moderate/strong MPO expression. The percent of MPO positive blasts in these two groups was similar. Expressions of CD15, CD117, and monocytic markers were more common in other MPAL than in B/myeloid MPAL^isoMPO . B/myeloid MPAL^isoMPO patients had similar overall and leukemia free survivals as B-ALL patients and better than other MPAL patients.

CONCLUSION

This is the first study to investigate the clinical significance of adult B/myeloid MPAL^isoMPO using the 2016 WHO classification. Our results suggest that B/myeloid MPAL^isoMPO clinically behaves more similarly to B-ALL than to other MPAL subtypes, supporting the 2016 WHO classification to segregate this entity from other MPAL subtypes.

International Consensus Classification of acute lymphoblastic leukemia/lymphoma

The updated International Consensus Classification (ICC) of B-acute lymphoblastic leukemia (B-ALL) and T-acute lymphoblastic leukemia (T-ALL) includes both revisions to subtypes previously outlined in the 2016 WHO classification and several newly described entities. The ICC classification incorporates recent clinical, cytogenetic, and molecular data, with a particular emphasis on whole transcriptome analysis and gene expression (GEX) clustering studies. B-ALL classification is modified to further subclassify BCR::ABL1-positive B-ALL and hypodiploid B-ALL. Additionally, nine new categories of B-ALL are defined, including seven that contain distinguishing gene rearrangements, as well as two new categories that are characterized by a specific single gene mutation. Four provisional entities are also included in the updated B-ALL classification, although definitive identification of these subtypes requires GEX studies. T-ALL classification is also updated to incorporate BCL11B-activating rearrangements into early T-precursor (ETP) ALL taxonomy. Additionally, eight new provisional entities are added to the T-ALL subclassification. The clinical implications of the new entities are discussed, as are practical approaches to the use of different technologies in diagnosis. The enhanced specificity of the new classification will allow for improved risk stratification and optimized treatment plans for patients with ALL.

Rapid and non-invasive discrimination of acute leukemia bone marrow supernatants by Raman spectroscopy and multivariate statistical analysis

A simple and non-invasive detection method for acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) was established by systematically investigating the characteristics of bone marrow supernatants from 61 AML patients, 22 ALL patients, and 5 volunteers without hematological tumors by Raman spectroscopy and orthogonal partial least squares discriminant analysis (OPLS-DA). The control group could be well distinguished from the AML and ALL groups by Raman peaks of 859, 1031, 1437, 1443, 1446, 1579, and 1603 cm^-1 and from the AML subtypes groups (AML-M2, AML-M3, AML-M4, and AML-M5) by the Raman peaks of 859, 1221, 1230, 1437, 1443, and 1603 cm^-1, indicating high sensitivity and specificity of the method. Potentially important variables of acute leukemia (AL) prognosis, such as cholesterol, high-density lipoprotein, low-density lipoprotein, adenosine deaminase, and hemoglobin, could be effectively identified by Raman peaks of 1437, 1443, and 1579 cm^-1. Therefore, Raman spectroscopy can be considered as a new non-invasive clinical tool for the detection of different types of AL and can be used to correlate biochemical parameters of AL patients with the classification and prognosis of AL.

Clinical features and prognosis of children with acute leukemias of ambiguous lineage under different diagnostic criteria

OBJECTIVES

To study the clinical features and prognosis of children with acute leukemias of ambiguous lineage (ALAL) under different diagnostic criteria.

METHODS

A retrospective analysis was performed on the medical data of 39 children with ALAL who were diagnosed and treated from December 2015 to December 2019. Among the 39 children, 34 received treatment. According to the diagnostic criteria for ALAL by World Health Organization and European Group for the Immunological Characterization of Leukemias, the 39 children were divided into two groups: ALAL group (n=28) and myeloid expression group (n=11). The clinical features, treatment, and prognosis were compared between the two groups.

RESULTS

The 34 children receiving treatment had a 3-year event-free survival (EFS) rate of 75%±9% and an overall survival rate of 88%±6%. The children treated with acute myeloid leukemia (AML) protocol had a 3-year EFS rate of 33%±27%, those treated with acute lymphoblastic leukemia (ALL) protocol had a 3-year EFS rate of 78%±10%, and those who had no remission after induction with AML protocol and then received ALL protocol had a 3-year EFS rate of 100%±0% (P<0.05). The children with negative minimal residual disease (MRD) after induction therapy had a significantly higher 3-year EFS rate than those with positive MRD (96%±4% vs 38%±28%, P<0.05). Positive ETV6-RUNX1 was observed in the myeloid expression group, and positive BCR-ABL1, positive MLL-r, and hyperleukocytosis (white blood cell count ≥50×109/L) were observed in the ALAL group. There was no significant difference in the 3-year EFS rate between the myeloid expression and ALAL groups (100%±0% vs 66%±11%, P>0.05).

CONCLUSIONS

ALL protocol has a better clinical effect than AML protocol in children with ALAL, and positive MRD after induction therapy suggests poor prognosis. Hyperleukocytosis and adverse genetic changes are not observed in children with myeloid expression, and such children tend to have a good prognosis, suggesting that we should be cautious to take it as ALAL in diagnosis and treatment.

Case Report: Myeloid Sarcoma Development During Treatment for B Cell Lymphoblastic Lymphoma in a Boy with KRAS/NRAS Gene Mutations

Here, we report a rare case of a 12-year-old boy who was initially diagnosed with B cell lymphoblastic lymphoma (BLBL) and developed myeloid sarcoma (MS) eight months after chemotherapy. Next-generation sequencing (NGS) showed mutations of KRAS and NRAS genes in both the bone marrow and lymph node. He presented an abnormal karyotype of 46, XY, -9, der (16) t (9; 16) (q13; q12), +mar. He received chemotherapy according to the South China Children's Leukemia Group 2016 protocol. Complete remission was achieved by the 15th day post-treatment. Eight months later and immediately prior to the start of maintenance therapy, the patient developed fever, skin nodules in both upper arms, and enlargement of bilateral testes. Pathological analysis of skin and testicular biopsies suggested the diagnosis of myeloid sarcoma (MS). Again, NGS examination showed mutations of KRAS and NRAS genes. The patient underwent haploidentical hematopoietic stem cell transplantation but unfortunately did not survive. The interval of eight-month interval between the initial disease onset and MS brings into question whether MS developed as part of the initial onset of disease or as a secondary tumor in association with chemotherapy. Thus, understanding the pathogenesis of MS involving abnormalities of lymphoid progenitors may assist in the prediction of prognosis and development of novel target therapies.