Lakhasly

Recent immunophenotypic studies of hairy cell leukemia (HCL) have suggested specific patterns of immunoreactiv- ity that may aid in diagnosis.We conclude that two-color flow cytometry with specific antibody combinations is an efficacious method for characterization and sensitive de- tection of hairy cells in PB. Application of the phenotypic criteria describedshould helpto increaseaccuracy indiag- nosis of HCL.We studied peripheral blood (PB)from 161 casesof HCLusingtwo-color direct immuno- fluorescenceflow cytometry and an extended panel of an- tibody combinations.Circulating hairy cells were identified by immunophenotypic features in 92% of the cases and could be detected even when representing ~ 1 of%circulat- ing lymphocytes.Based on these features, HCL waseasilydistinguishedfrom50casesofchroniclympho- cytic leukemia (CLL).The 133 cases with 22% detectable hairy cells were analyzed in detail.

Recent immunophenotypic studies of hairy cell leukemia (HCL) have suggested specific patterns of immunoreactiv- ity that may aid in diagnosis. We studied peripheral blood (PB)from 161 casesof HCLusingtwo-color direct immuno- fluorescenceflow cytometry and an extended panel of an- tibody combinations. Circulating hairy cells were identified by immunophenotypic features in 92% of the cases and could be detected even when representing ~ 1 of%circulat- ing lymphocytes. The 133 cases with 22% 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 in- tense, uniform expressionof C D l lc, with CD19; (3)mod- erately intense staining for CD25, with CD19; (4) very in- tense staining for CD22; (5) moderate to very intense staining for CD20; and (6) moderately intense monoclonal surface lg. Phenotypic variability existed in expression of CD10 (26%)and CD5 (4%). Based on these features, HCL waseasilydistinguishedfrom50casesofchroniclympho- cytic leukemia (CLL). Although CLL exhibited frequent ex- pression of C D l l c (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 lg. 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 de- tection of hairy cells in PB. Application of the phenotypic criteria describedshould helpto increaseaccuracy indiag- nosis of HCL.