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Diagnostic application of two-color flow cytometry in 161 cases of hairy cell leukemia
B A Robbins1, D J Ellison, J C Spinosa
1Department of Pathology, Scripps Clinic and Research Foundation, La Jolla, CA 92037.
Insights
Flow cytometry using specific antibodies accurately identifies hairy cell leukemia (HCL). This method detects hairy cells in peripheral blood (PB) and distinguishes HCL from chronic lymphocytic leukemia (CLL).
Area of Science:
- Hematology
- Immunology
- Oncology
Background:
- Immunophenotypic studies offer insights into hairy cell leukemia (HCL) diagnosis.
- Flow cytometry is a key technique for analyzing cell surface markers.
Purpose of the Study:
- To establish reliable immunophenotypic criteria for diagnosing HCL in peripheral blood.
- To differentiate HCL from chronic lymphocytic leukemia (CLL) using flow cytometry.
Main Methods:
- Analysis of peripheral blood from 161 HCL cases using two-color direct immunofluorescence flow cytometry.
- Utilized an extended panel of antibody combinations to identify hairy cell surface markers.
- Compared immunophenotypic profiles of HCL with 50 cases of CLL.
Main Results:
- HCL exhibits a unique B-cell phenotype: B-ly7+, CD19+, intense CD11c+, moderate CD25+, intense CD22+, moderate/intense CD20+, and monoclonal surface Ig.
- Hairy cells were detected in 92% of HCL cases, even at low percentages (< or = 1%).
- B-ly7 was highly specific for HCL, absent in all CLL cases, aiding differentiation.
Conclusions:
- Two-color flow cytometry with specific antibody combinations is effective for HCL characterization and detection in PB.
- Established phenotypic criteria enhance diagnostic accuracy for HCL.
- The study provides a robust method for distinguishing HCL from CLL based on distinct immunophenotypic profiles.
Abstract:
Recent immunophenotypic studies of hairy cell leukemia (HCL) have suggested specific patterns of immunoreactivity that may aid in diagnosis. We studied peripheral blood (PB) from 161 cases of HCL using two-color direct immunofluorescence flow cytometry and an extended panel of antibody combinations. Circulating hairy cells were identified by immunophenotypic features in 92% of the cases and could be detected even when representing < or = 1% of circulating lymphocytes. The 133 cases with > or = 2% detectable hairy cells were analyzed in detail. HCL showed a uniform and unique B-cell phenotype, with each of the following features identified in 99% to 100% of cases: (1) positive staining for B-ly7, coexpressed with CD19; (2) very intense, uniform expression of CD11c, with CD19; (3) moderately intense staining for CD25, with CD19; (4) very intense staining for CD22; (5) moderate to very intense staining for CD20; and (6) moderately intense monoclonal surface Ig. Phenotypic variability existed in expression of CD10 (26%) and CD5 (4%). Based on these features, HCL was easily distinguished from 50 cases of chronic lymphocytic leukemia (CLL). Although CLL exhibited frequent expression of CD11c (74%) and CD25 (68%), the intensity of staining was significantly less than HCL. Furthermore, CLL was uniformly positive for CD5 and showed weak staining for CD20, CD22, and surface Ig. B-ly7 proved to be the most specific marker, reacting with 100% of HCL cases, but absent in all cases of CLL. We conclude that two-color flow cytometry with specific antibody combinations is an efficacious method for characterization and sensitive detection of hairy cells in PB. Application of the phenotypic criteria described should help to increase accuracy in diagnosis of HCL.