Aberrant Immunophenotypes Detected by Flow Cytometry in Acute Lymphoblastic Leukemia

Abstract

The present study was designed to analyse the proportion of ALL patients in which the phenotypic detection of minimal residual disease (MRD) is feasible, based on the presence of aberrant phenotypes: lineage infidelity, asynchronous expression, overexpression and ectopic phenotype. For this purpose we have prospectively investigated the phenotype of blast cells from 25 patients at diagnosis using a large panel of monoclonal antibodies by multiparametric flow cytometry. The mean age was 23.3 × 17.3 with 10 children and 15 adults. 14 patients were classified as L1, 9 L2 and 2 L3 according to the FAB classification. 17 cases were B-lineage ALL and 8 T-ALL. 23 out of 25 cases (92%) included in this study displayed phenotypic aberrations at diagnosis (15 out of 17 cases of B-lineage ALL and all T-ALL patients). 76% of patients displayed two or more than two aberrancies. The phenotypic aberrations were lineage infidelity, found in 12 patients, asynchronous antigen expression detected in 17 patients, antigen overexpression in 4 patients and ectopic phenotype in 7 patients.

In summary our results show that when a large panel of MoAbs is used for the immunophenotypical characterization of ALL, most patients display aberrant phenotypes, the coexistence of more than two aberrant antigen expressions being frequently detected. These results suggest that the use of immunological methods for the detection of MRD in ALL based on the existence of aberrant phenotypes could be of great help for the follow-up of patients in complete remission.

Key Words:

• ALL
• immunophenotype
• minimal residual disease