Flow cytometric analysis of lymphoid enhancer-binding factor 1 in diagnosis of chronic lymphocytic leukemia/small lymphocytic lymphoma

Downregulation of Lymphoid enhancer-binding factor 1 (LEF-1) expression (by immunohistochemistry and/ flow cytometry) in chronic Lymphocytic Leukemia with atypical immunophenotypic and cytologic features

INTRODUCTION

Lymphoid enhancer-binding factor 1 (LEF-1) overexpression has been recently remarkably reported in chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) and has shown utility in distinguishing CLL/SLL from other B-cell lymphomas. CLL has a well-defined immunophenotype, yet, some cases of CLL demonstrate atypical morphology/ phenotype reflected by low Matutes score (atypical CLL). Till date, LEF1 expression has not been systematically studied in cases of CLL with atypical features.

METHODS

In this study, LEF-1 expression was assessed by two different techniques, (immunohistochemistry and flow cytometry), to investigate the expression profile of LEF-1 in cases of CLL/SLL, in comparison with other low-grade B-lymphomas and CLL with atypical features, including atypical immunophenotype and CLL with increased prolymphocytes or morphologically atypical cells.

RESULTS

We found that LEF-1 expression is downregulated in CLL with atypical immunophenotype/features compared to classic CLL; Chi-Square P < .0001. The ratio for LEF-1 expression in malignant B-cells/NK (by flow cytometry) in CLL/SLL with classic immunophenotype was higher than atypical CLL and is significantly higher in other small B-cell lymphomas (P < .01). Absence of LEF-1 expression in CLL/SLL is correlated (P < .05) with downregulation of CD5, CD23, CD200, expression of FMC7, brighter expression of CD79b, brighter expression of surface light chain, increased prolymphocytes and lower Matutes score.

CONCLUSION

As downregulation of LEF-1 expression is well correlated with atypical CLL, we suggest adding LEF-1 to Matutes score as a beneficial marker to differentiate classic from atypical CLL LEF-1 could also serve as a potential prognostic indicator for CLL clinical course.

The current role of clinical flow cytometry in the evaluation of mature B-cell neoplasms

Flow cytometry (FC) has a well-established role in the diagnostic evaluation of mature B-cell neoplasms. Effective assessment for lineage associated antigens, aberrant antigen expression, and immunoglobulin light chain restriction requires a well-designed, optimized, and controlled FC assay. However, it is important for hematopathologists to know when flow cytometry has a more limited role, and other modalities, such as immunohistochemistry, cytogenetic and molecular testing, are more important. This review will discuss the features of an optimal FC assay for the evaluation of mature B-cell neoplasms, and the current role of FC in the diagnosis and sub-classification, prognostic assessment, identification of therapeutic targets, and assessment for disease response to therapy. © 2018 International Clinical Cytometry Society.

Diagnostic Utility of Lymphoid Enhancer Binding Factor 1 Immunohistochemistry in Small B-Cell Lymphomas

OBJECTIVES

Recent studies have shown that lymphoid enhancer binding factor 1 (LEF1) is a useful marker for chronic lymphocytic B-cell leukemia (CLL)/small lymphocytic lymphoma. Yet, it is not still being widely used in a diagnostic setting. In this study, we document the experience with LEF1 immunohistochemistry during routine diagnostics.

METHODS

In total, 191 B-cell lymphoma cases from Hammersmith Hospital, Imperial College NHS Healthcare Trust (London, UK) were investigated by immunohistochemistry for LEF1 during routine diagnostic workup. These cases included both bone marrow trephines and lymph node biopsy specimens. The monoclonal antibody clone EPR2029Y was used.

RESULTS

LEF1 expression was strong and diffuse (>70% of cells) in most cases. Few CLL cases showed a staining in proliferation centers only. Seventy-seven of 80 CLL cases expressed LEF1. Other entities expressing LEF1 included one of 38 follicular lymphomas, two of 33 marginal zone lymphomas, and one diffuse large B-cell lymphoma with a background of follicular lymphoma grade 3B. Sensitivity for LEF1 for the diagnosis of CLL was 0.96, and specificity was 0.93.

CONCLUSIONS

In this study, we could demonstrate the diagnostic utility of LEF1. LEF1 is a sensitive and specific marker for CLL and is helpful in the diagnosis of diagnostically challenging small B-cell lymphomas.

Lymph Node Fine-Needle Cytology of Non-Hodgkin Lymphoma: Diagnosis and Classification by Flow Cytometry

In the last decades, lymph node fine-needle cytology (FNC), coupled with flow cytometry (FC), has gained a role in the diagnosis and classification of non-Hodgkin lymphoma (NHL). The combination of FNC/FC allows the diagnosis and classification of NHL in lymph node samples with a high sensitivity and specificity by combining cytological features and specific phenotypic profiles. The present review provides a brief technical description of FC and a detailed analysis of the current markers and their combinations (diagnostic algorithm) for the diagnosis and classification of NHL. The basic principles of clonality assessment, as well as the diagnostic strengths and weaknesses of the procedure, are reported. The current diagnostic algorithms for NHL classification are critically reviewed with a focus on specific problems related to single entities. Moreover, this review provides a detailed analysis of the different clinical contexts in which FNC/FC is performed and related implications. Future and further applications of FNC/FC for NHL are also discussed.

Issues in diagnosis of small B cell lymphoid neoplasms involving the bone marrow and peripheral blood. Report on the Bone Marrow Workshop of the XVIIth meeting of the European Association for Haematopathology and the Society for Hematopathology

Small B cell lymphoid neoplasms are the most common lymphoproliferative disorders involving peripheral blood (PB) and bone marrow (BM). The Bone Marrow Workshop (BMW) organized by the European Bone Marrow Working Group (EBMWG) of the European Association for Haematopathology (EAHP) during the XVIIth EAHP Meeting in Istanbul, October 2014, was dedicated to discussion of cases illustrating how the recent advances in immunophenotyping, molecular techniques and cytogenetics provide better understanding and classification of these entities. Submitted cases were grouped into following categories: (i) cases illustrating diagnostic difficulties in chronic lymphocytic leukaemia (CLL); (ii) cases of BM manifestations of small B cell lymphoid neoplasms other than CLL; (iii) transformation of small B cell lymphoid neoplasms in the BM; and (iv) multiclonality and composite lymphomas in the BM. This report summarizes presented cases and conclusions of the BMW and provides practical recommendations for classification of the BM manifestations of small B cell lymphoid neoplasms based on the current state of knowledge.

Characterization of LEF1 High Expression and Novel Mutations in Adult Acute Lymphoblastic Leukemia

Aberrant activation of the Wnt pathway plays a pathogenetic role in tumors and has been associated with adverse outcome in acute lymphoblastic leukemia (ALL). Lymphoid enhancer binding factor 1 (LEF1), a key mediator of Wnt signaling, has been linked to leukemic transformation, and LEF1 mutations have been identified in T-ALL. Here we found LEF1 is highly expressed in 25.0% adult ALL patients and LEF1 high expression was associated with high-risk leukemia factors (high WBC, Philadelphia chromosome positive, complex karyotype), shorter event-free survival (EFS), and high relapse rates in patients with B-ALL. LEF1 high expression is also associated with high mutation rate of Notch1 and JAK1 in T-ALL. We identified 2 novel LEF1 mutations (K86E and P106L) in 4 of 131 patients with ALL, and those patients with high-risk ALL (high WBC, complex karyotype). These results suggest a role for LEF1 mutations in leukemogenesis. We further explored the effect of the mutations on cell proliferation and found both mutations significantly promoted the proliferation of ALL cells. We also observed the effect of LEF1 and its mutations on the transcription of its targets, c-MYC and Cyclin D1. We found LEF1 increased the promoter activity of its targets c-MYC and Cyclin D1, and LEF1 K86E and P106L mutants further significantly enhanced this effect. We also observed that the c-MYC and Cyclin D1 mRNA levels were significantly increased in patients with LEF1 high expression compared with those with low expression. Taken together, our findings indicate high LEF1 expression and mutation are associated with high-risk leukemia and our results also revealed that LEF1 high expression and/or gain-of-function mutations are involved in leukemogenesis of ALL.