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.