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Published on: March 26, 2018
Hairy cell leukemia: early immunophenotypical detection and quantitative analysis by flow cytometry
1Cancer Research Institute; Slovak Academy of Sciences, 833 91 Bratislava, Slovak Republic. exonobab@savba.sk
Insights
Flow cytometry effectively detects low-level hairy cell leukemia (HCL) cells in blood and bone marrow. Quantitative immunophenotyping aids in distinguishing HCL from normal cells, crucial for early diagnosis and minimal residual disease monitoring.
Area of Science:
- Hematology
- Immunology
- Oncology
Background:
- Hairy cell leukemia (HCL) is characterized by abnormal B-lymphocyte markers.
- Detecting low neoplastic cell levels is crucial for early diagnosis and minimal residual disease (MRD) assessment in HCL.
Purpose of the Study:
- To evaluate the utility of flow cytometric immunophenotyping for early HCL diagnosis and MRD detection.
- To determine if quantitative immunophenotyping (MESF) can differentiate HCL cells from normal B-cells at low levels.
Main Methods:
- Analysis of 174 specimens from 19 HCL patients using flow cytometry.
- Quantitative immunophenotyping with fluorescent calibration microbeads to measure marker density (MESF).
- Evaluation of CD4+ T-cell counts post-treatment.
Main Results:
- Flow cytometry detected low levels of malignant cells in HCL patients at diagnosis and during MRD monitoring.
- Quantitative analysis of MESF values showed higher marker density on HCL cells compared to normal B-cells.
- Complete remission was observed in 67% of treated patients; 33% showed transient MRD+ phenotype.
Conclusions:
- Flow cytometry is a sensitive and specific method for detecting low-level malignant cells in HCL.
- Quantitative immunophenotyping (MESF) offers a reliable marker for HCL detection, even with small cell numbers.
- Persistent CD4+ lymphopenia after treatment correlates with a lower incidence of clinical HCL progression.
Unlabelled:
The abnormal coexpression of the so-called 'HCL-restricted' markers (CD22+CD11c, CD25 and CD103) identified on monotypic, slightly large B-lymphocytes in the large cell-gate of dot-plots has previously been shown to be highly characteristic of hairy cell leukemia (HCL). The main aim of our present study was to determine if patterns with low levels of neoplastic cells in bone marrow (BM) or peripheral blood (PB) are of a value the early diagnosis and/or detection of minimal residual disease (MRD) in HCL. Next we wished to determine if quantitative immunophenotyping given by molecules of equivalent soluble fluoresceine (MESF) could help to distinguish pathologic B-lymphocytic pool from that of normal residual B-cells also in patients with low numbers of HCL cells. The abnormal immunophenotypes were studied in 174 specimens from 19 patients with suspect HCL or during follow-up of already treated patients. For evaluation of marker density fluorescent calibration microbeads were used. In 12 HCL patients (67%) permanent complete remission was observed after treatment. In 6 patients (33%) transient MRD+ phenotype was identified but the clinical manifestation of relapse was followed till now in only three patients. One patient was phenotyped just only at diagnosis. The pathological cells in low levels were found in 5 patients at diagnosis (in the range from 2 to 12%) and in patients with MRD+ phenotype they were recognized repeatedly in the range from 2 to 8%. Furthermore, we observed in hairy cells significantly higher values of molecule numbers of some B-cell markers, comparing to that of residual B-cells in nonleukemic lymphocyte gate of the same sample. We found profound and persistent CD4+ lymphopenia in all but one studied patients after CdA treatment.
Conclusions:
Flow cytometric immunophenotyping of PB and BM is highly sensitive and specific method and is capable to detect low levels of malignant cells in HCL. Quantitative analysis of MESF values of pathological B-cells comparing to normal residual B-cells seems to be another new marker of HCL in common, which is reliable detecting also small cell numbers in examined sample. A long-term decline of CD4+ T-cells correlated with the relatively low incidence of clinical progression of HCL.
