International cooperative study identifies treatment strategy in childhood ambiguous lineage leukemia

Despite attempts to improve the definitions of ambiguous lineage leukemia (ALAL) during the last 2 decades, general therapy recommendations are missing. Herein, we report a large cohort of children with ALAL and propose a treatment strategy. A retrospective multinational study (International Berlin-Frankfurt-Münster Study of Leukemias of Ambiguous Lineage [iBFM-AMBI2012]) of 233 cases of pediatric ALAL patients is presented. Survival statistics were used to compare the prognosis of subsets and types of treatment. Five-year event-free survival (EFS) of patients with acute lymphoblastic leukemia (ALL)-type primary therapy (80% ± 4%) was superior to that of children who received acute myeloid leukemia (AML)-type or combined-type treatment (36% ± 7.2% and 50% ± 12%, respectively). When ALL- or AML-specific gene fusions were excluded, 5-year EFS of CD19⁺ leukemia was 83% ± 5.3% on ALL-type primary treatment compared with 0% ± 0% and 28% ± 14% on AML-type and combined-type primary treatment, respectively. Superiority of ALL-type treatment was documented in single-population mixed phenotype ALAL (using World Health Organization and/or European Group for Immunophenotyping of Leukemia definitions) and bilineal ALAL. Treatment with ALL-type protocols is recommended for the majority of pediatric patients with ALAL, including cases with CD19⁺ ALAL. AML-type treatment is preferred in a minority of ALAL cases with CD19^- and no other lymphoid features. No overall benefit of transplantation was documented, and it could be introduced in some patients with a poor response to treatment. As no clear indicator was found for a change in treatment type, this is to be considered only in cases with ≥5% blasts after remission induction. The results provide a basis for a prospective trial.

Mixed-Phenotype Acute Leukemia: Diagnostic Criteria and Pitfalls

Mixed-phenotype acute leukemia (MPAL) is a heterogeneous category in the World Health Organization classification that comprises acute leukemias with discrete admixed populations of myeloid and lymphoid blasts (“bilineal”) or with extensive coexpression of lymphoid and myeloid markers in a single blast population (“biphenotypic”). Flow cytometric findings suggestive of MPAL are often met with consternation by pathologists and oncologists alike, owing to unfamiliarity with the disease and uncertainty about how MPAL fits into established paradigms for treatment of acute leukemia. The purpose of this review is to explain the diagnostic criteria for MPAL, summarize its biological and clinical features, and address common diagnostic pitfalls of these unusual leukemias.

Comparison of Immunohistochemistry, Cytochemistry, and Flow Cytometry in AML for Myeloperoxidase Detection

Acute Myeloid Leukemia (AML) as per World Health Organization (WHO 2008) classification is on the basis of the antigenic characterization, enzymes restriction in the neoplastic myeloid cells and the specific translocations/mutations. AML can be assessed and differentiated by flowcytometry (FCM)/immunohistochemistry (IHC)/cytochemistry techniques. Myeloperoxidase (MPO) is an unequivocal marker to differentiate AML from the acute lymphoblastic leukemia. Despite FCM popularity, it has its limitations, in form of 'dry-tap', cost, and inability of being performed by retrospective analysis. IHC, though an old technique has overcome these disadvantages of FCM. Cytochemistry, on the other hand has its own advantages in being cost-effective; technically easy to do while its disadvantages are its inability to be carried out in the old samples, 'dry-tap' conditions in aleukemic leukemia. There has been non-uniformity in the literature among these techniques especially concerning their sensitivity for MPO. A prospective study was done at All India Institute of Medical Sciences New Delhi from 01 July 2014 to 30 Nov 2015 to include 120 diagnosed acute myeloid leukemia cases. Myeloperoxidase stain was done by cytochemistry, immunohistochemistry and flow cytometry and results were compared. There were 28 cases which showed discrepancies. Out of these 28 cases immunohistochemistry showed positivity in majority (22 cases) followed by flow cytometry (14 cases). Therefore it is important to employ more than one technique and IHC must be included for detection of MPO in all suspected cases of AML especially when negative with FCM .

Haematological profile of patients with mixed-phenotype acute leukaemia from a tertiary care centre of north India

Background & objectives:

Mixed-phenotype acute leukaemia (MPAL) is a rare neoplasm with no definite treatment protocols and a distinctly poor outcome. Advancement in polychromatic flow cytometry has made its identification easier. This prospective study was designed to identify cases of MPAL and study their clinical presentation and haematological profile in a tertiary care hospital in north India.

Methods:

Ethylenediaminetetraacetic acid (EDTA)-anticoagulated bone marrow aspirate samples of patients diagnosed as acute leukaemia (AL) on the basis of morphology were utilized for immunophenotyping. A comprehensive panel of fluorochrome-labelled monoclonal antibodies targeting myeloid, B-cell, T-cell and immaturity markers was utilized. The patients diagnosed to have MPAL, on the basis of the World Health Organization 2008 classification, were selected for further analyses.

Results:

There were 15 (2.99%) patients with MPAL of the total 501 cases of AL. Seven were children, all males and mean age of 5.08±3.88 yr. Eight were adults, male:female=6:2 and mean age of 21.43±5.74 yr. Eight were diagnosed as B/myeloid and seven were T/myeloid. No association was observed between age and immunophenotype of MPAL. On morphology, 11 were diagnosed as AML and four as ALL, and no specific morphology of blasts was predictive of a MPAL.

Interpretation & conclusions:

MPAL appeared to be a rare neoplasm (2.99% of AL cases). A comprehensive primary panel of monoclonal antibodies should be used to identify this neoplasm known to have a poor outcome.

Clinical Significance of Isolated Myeloperoxidase Expression in Pediatric B-Lymphoblastic Leukemia

Objectives

Diagnosis of B-cell acute lymphoblastic leukemia (B-ALL) requires immunophenotypic evidence of B-lineage and absence of specific myeloid or T-lineage markers. Rare cases of otherwise typical B-ALL express myeloperoxidase (MPO) detectable by flow cytometry with an absence of other myeloid markers, but the clinical significance of this finding is not well studied.

Methods

A retrospective cohort analysis of flow cytometry and clinical data was performed to investigate the clinical outcome of this specific group of patients.

Results

Twenty-nine cases of otherwise typical B-ALL that expressed MPO by flow cytometry (B-ALL-isoMPO) without expression of other myeloid markers were identified. The B-ALL-isoMPO group had a significantly increased incidence of relapse (univariate log rank P  = .0083; multivariate hazard ratio, 2.50; 95% confidence interval, 1.07-5.85; P  = .034) and significantly worse event-free survival by univariate analysis (log rank P  = .0066) compared with a reference group of patients with B-ALL from the same time period (n = 264).

Conclusions

To our knowledge, this is the first report to document the clinical outcomes in a group of pediatric patients with B-ALL that expresses MPO in the absence of other myeloid markers. This group had an increased rate of relapse and a worse event-free survival than the patients with B-ALL who did not express MPO.

[Expression of cMPO in 502 cases of acute myeloid leukemia (AML) and its diagnosis significance in AML subtypes]

目的

探讨髓过氧化物酶（cMPO）在急性髓系白血病（AML）患者中的表达及其在诊断分型中的意义。

方法

采用CD45/SSC双参数散点图设门方法对502例AML患者进行八色流式细胞术免疫表型分析，观察患者白血病细胞cMPO表达的阳性率和阳性强度。

结果

502例AML患者cMPO总体阳性率为58.0%，其中阳性占21.5%，弱阳性占34.1%，部分阳性占2.4%；阴性占42.0%。各亚型中，AML伴t(15;17）（q22;q12）/PML-RARα的cMPO阳性率最高，为100%，阳性强度多数接近正常粒细胞水平；其次为AML伴t(8;21）（q22;q22）/RUNX1-RUNX1T1，阳性率为91.4%，阳性强度多为弱阳性；AML微分化型和急性巨核细胞白血病患者cMPO表达皆为阴性；余各亚型阳性率在22.7%~76.2%。

结论

各亚型AML cMPO的阳性率及阳性强度存在显著差异。

B-acute lymphoblastic leukemia/lymphoblastic lymphoma

OBJECTIVES

This session of the 2013 Society of Hematopathology/European Association for Haematopathology Workshop was dedicated to B-acute lymphoblastic leukemia (B-ALL)/lymphoblastic lymphoma (LBL) with recurrent translocations and not otherwise specified.

METHODS

In this review, we summarize the cases discussed during the workshop, review the pertinent and most recent literature on the respective topics, and provide a few key points that may aid in the workup of patients with B-ALL/LBL.

RESULTS

Many of the submitted cases showed interesting diagnostic, immunophenotypic, or clinical aspects of B-ALL with BCR/ABL1, MLL-associated, and other recurrent chromosomal abnormalities. Several cases showed rare aberrancies such as coexistent IGH/BCL2 and MYC rearrangements and raised issues in classification. Other cases had unusual clinical presentations, including B-ALL with hypereosinophilia and therapy-related B-ALL. Several cases highlighted the role of flow cytometry immunophenotyping in distinguishing benign B-cell precursors from aberrant lymphoblasts, and other cases raised questions regarding the clinical importance of myeloperoxidase positivity in acute lymphoblastic leukemia.

CONCLUSIONS

The complexity and spectrum of cases presented in this review highlight the importance of clinicopathologic correlation and the value of ancillary studies in the classification and workup of patients with B-ALL/LBL.

Acute leukemias of ambiguous origin

OBJECTIVES

This session of the Society for Hematopathology/European Association for Haematopathology Workshop focused on acute leukemias of ambiguous origin.

METHODS

We provide an overview of mixed-phenotype acute leukemia (MPAL) as recognized in the current World Health Organization classification and summarize diagnostic criteria for major categories of MPAL: B/myeloid, T/myeloid, B/T, and B/T/myeloid.

RESULTS

Most MPAL cases submitted were B/myeloid and T/myeloid MPAL, the most frequent types, but three cases of B/T MPAL were also submitted, and examples of all categories are illustrated. We emphasize that a comprehensive approach to immunophenotyping is required to accurately establish the diagnosis of MPAL. Flow cytometry immunophenotyping using a large panel of antibodies is needed as well as confirmatory immunohistochemical analysis and cytochemistry studies for myeloperoxidase and nonspecific esterase. We discuss technical issues in determining blast lineage and possible pitfalls in MPAL diagnosis. In particular, rare cases of B-acute lymphoblastic leukemia (B-ALL) can express myeloperoxidase but are otherwise consistent with B-ALL and should be treated as such. Last, we review the differential diagnosis between acute undifferentiated leukemia and acute myeloid leukemia with minimal differentiation.

CONCLUSIONS

There was an agreement that diagnosis of MPAL can be challenging, especially if applied flow cytometry panels are not comprehensive enough.

Can threshold for MPO by flow cytometry be reduced in classifying acute leukaemia? A comparison of flow cytometric and cytochemical myeloperoxidase using different flow cytometric cut-offs

Objectives Myeloperoxidase (MPO) detection either by enzyme cytochemistry (cMPO) or flow cytometry (fMPO) plays a major role in acute leukaemia (AL) diagnosis as per World Health Organization (WHO) 2008 classification. Although 3% cMPO was recommended as positivity, no specific cut-off had been mentioned by WHO for fMPO. Various authors recommend different cut-offs ranging from 3 to 28% for fMPO. The aim of this study was to analyse fMPO cut-offs ranging from 3 to 10% in classifying AL and to assess whether a new cut-off could be suggested. Methods Totally, 216 cases of AL were retrospectively analysed for fMPO ranging from 3 to 10% and compared with gold standard. Presence of cMPO (≥3%) and/or expression of two or more pan-myeloid markers (CD13, CD33, and CD117) in the absence of CD19 and CD3 were kept as gold standard for diagnosis of acute myeloid leukaemia (AML). Results Sensitivities for classifying AL as AML/mixed phenotypic acute leukaemia (MPAL) at 3, 5.4, and 10% were 98.3, 98.3, and 96.6%, respectively, whereas specificities at this cut-off were 22.2, 91, and 71%, respectively. Discussion Only few studies have been done in this aspect to define a consistent cut-off for fMPO for proper classification of acute leukaemias. This was one of the largest and few studies available till date in this regard. Conclusion The newer cut-off for fMPO (5.4%) emerged out from our study with best sensitivity and specificity for accurately classifying AL cases into acute lymphoblastic leukaemia, AML, and MPAL.