CD200 flow cytometric assessment and semiquantitative immunohistochemical staining distinguishes hairy cell leukemia from hairy cell leukemia-variant and other B-cell lymphoproliferative disorders.

OBJECTIVES To evaluate CD200 expression in B-cell proliferative disorders. METHODS We analyzed 180 recent specimens of B-cell neoplasms for CD200 expression by flow cytometric immunophenotypic analysis, which is better able to assess relative intensity of staining than immunohistochemical staining. RESULTS We found that hairy cell leukemia exhibits a high level of staining for CD200 in comparison to other B-cell lymphoproliferative disorders, including hairy cell leukemia-variant (HCL-V), marginal zone lymphoma, and lymphoplasmacytic lymphoma. We confirmed this observation by semiquantitative immunohistochemical staining. CONCLUSIONS Assessment of the CD200 expression level is helpful to distinguish HCL from HCL-V and other B-cell lymphoproliferative disorders and in the differential diagnosis of B-cell neoplasms in general.