Role of CD200 in differential diagnosis of mature B-cell neoplasm

Introduction: CD 200 is a type I immunoglobulin super family membrane glycoprotein, which is expressed in various mature B-cell neoplasm (MBN). This study aimed at analyzingthe expression pattern of CD200 by flow cytometry immunophenotyping (FCI) and to evaluate its utility in narrowing down the differential diagnosis of MBN, particularly in low-grade lymphomas. Methods: A total of 160 samples were evaluated by FCI over a period of 2 years (July 2014-June 2016), by a panel of antibodies including CD200. The mean fluorescence intensity (MFI) of CD200 in the neoplastic population was noted and compared among several groups of MBN. Results: All the 98 cases of chronic lymphocytic leukemia (CLL), five being CD23-negative, expressed CD200 with moderate-to-bright intensity (median MFI: 1174). None of the 24 mantle cell lymphoma (MCL) cases, two being CD23-positive, expressed CD200 (median MFI: 10). All six hairy cell leukemia (HCL) cases expressed CD200. CD200 expression in HCL was brightest among all the MBNs, with a median MFI of 5050. Other MBN (n = 32) expressed CD200 in a proportion of cases and with variable intensity, usually dimmer than CLL. Conclusion: CD200 has a valid role in differentiating CLL from MCL, especially in the cases with immunophenotypic overlap. HCL has a consistent and brightest expression of CD200. It would be prudent to include CD200 in the primary panel of antibodies for MBN analysis.