Utility of CD200 expression by flow cytometry in lymphoproliferative disorders and plasma cell dyscrasias

Background: The cluster of differentiation 200 (CD200) is a recently introduced marker, used to differentiate various lymphoproliferative disorders (LPDs) and is a potential target for chemotherapy. Objective: The objective is to study the utility of CD200 expression by flow cytometry (FC) in various LPDs and plasma cell disorders. Materials and Methods: This is a retrospective study done over a period of 2 years. The study group included 52 cases with a clinical suspicion of LPD (n = 40) or plasma cell disorder (n = 12). Clinical data, morphological data on peripheral blood, and/or bone marrow examination were analyzed and correlated with the final results on FC. Results: Out of 40 LPDs, chronic lymphocytic leukemia (CLL) accounted for a majority of the cases accounting for 57.5% (23 cases). Plasma cell myelomas (PCM) were the most common plasma cell disorders accounting for 75% (nine cases). All cases of CLL showed CD200 expression and the two cases of mantle cell lymphoma (MCL) were CD200 negative. Splenic marginal zone lymphomas (MZL) involving marrow showed dim CD200 expression. Bright CD200 expression was also observed in all cases of hairy cell leukemia (HCL) and 67% of cases diagnosed as PCM. Conclusion: CD200 is a very useful marker in the diagnosis of various LPDs especially CLL, HCL, and PCMs. It can be used as an additional marker particularly in distinguishing CLL/small lymphocytic lymphoma (SLL) from MCL and atypical CLL from other CD5+ B-cell neoplasms and extranodal MZL.