CD52 expression in hairy cell leukemia.

Hairy cell leukemia (HCL) is a rare chronic B-cell lymphoproliferative disorder characterized by splenomegaly, pancytopenia, and circulating atypical lymphocytes with circumferential cytoplasmic projections. Although uncommon, HCL cases refractory to standard therapy occur, and effective alternatives are limited. There is evolving literature supporting monoclonal antibody therapy in the treatment of B-cell lymphoid malignancies, including anti-CD52 (Campath-1H, alemtuzumab). We have examined nine cases of HCL and one case of HCL variant by flow cytometry for CD52 expression. All cases expressed CD52 antigen in 92-100% of the malignant cells. The demonstration of CD52 antigen expression on HCL cells provides the rationale for the use of alemtuzumab in refractory HCL.