The role of immunophenotyping in differential diagnosis of chronic lymphocytic leukemia

Abstract

Introduction: Accurate diagnosis of chronic lymphocytic leukemia (CLL) acquires immunophenotyping by flow cytometry in order to facilitate differential diagnosis between CLL and other mature B-cell neoplasms (MBCN). Objective: The aim of this study was to define immunological profile of CLL cells. Methods: Immunophenotyping by flow cytometry was performed on peripheral blood specimens at diagnosis in the group of 211 patients with de novo MBCN. Results: Absolute count of B-cells was significantly increased in all MBCN patients comparing to healthy control group (p<0.05). B-cell monoclonality was detected in 96% of all MBCN patients, by using surface immunoglobulin (sIg) light chain restriction. B-cell antigens, CD19, CD20, CD22, were expressed with very high frequency in CLL and other MBCN. In comparison with other MBCN, in CLL group, the frequency of expression was higher for CD5 and CD23 (p<0.0001), though lower for FMC7 antigen (p<0.0001). CLL patients were characterized by lower expression patterns of CD20, CD22, CD79b, and sIg (p<0.0001) as well as higher expression pattern of CD5 antigen (p<0.05). Correlation between the final diagnosis of MBCN and values of CLL scoring system showed that the majority of CLL patients (97%) had higher values (5 or 4) whereas the majority of other MBCN patients (96%) had lower score values (0-3). Conclusion: Our results have shown that characteristic immunophenotype which differentiates CLL from other MBCN is defined by following marker combination - CD19⁺ CD20^+low CD22^+low CD5^+high CD23⁺ FMC7- CD79b^+low sIg^+low. CLL score values of 5 or 4 points are highly suggestive for diagnosis of CLL.