Immunophenotype of hairy‐cell leukemia

Abstract
15 cases of HCL were studied with a panel of monoclonal antibodies against different leukocyte antigens. A B‐cell phenotype different from that of B‐CLL was observed (CD10, CD19+, CD20+, CD21, CD22+, CD37+, CD38, FMC7+, LN1+, PCA‐1+, BLy7+and CD5). As expected, CD11c and CD25 were positive and, in addition, a My7 and My9 positivity in varying degree was noted. 3 weeks of in vitro incubation did not significantly alter the phenotype. We conclude that HCL exhibits a unique phenotype among chronic B‐cell leukemias, which is closer to the plasma cell stage of differentiation than that of B‐CLL. The BLy7 monoclonal antibody seems to be a promising marker for HCL.