[1386] CD200 Is a Valuable Diagnostic Tool To Differentiate Mediastinal Large B-Cell Lymphoma from Diffuse Large B-Cell Lymphoma

Aparna Hariharan, Juan Gomez-Gelvez, Kedar V Inamdar. Henry Ford Hospital, Detroit, MI

Background: CD200 is a type I immunoglobulin superfamily membrane glycoprotein expressed in a variety of B-lymphoid neoplasms including chronic lymphocytic leukemia/small lymphocytic lymphoma, hairy cell leukemia as well as Hodgkin lymphomas. Its utility in large cell neoplasms however largely remains underexplored. Very few studies to date have looked at CD200 in large B-cell neoplasms including diffuse large B-cell lymphoma (DLBCL) and mediastinal large B-cell lymphomas (MBCL). In this study we assessed the expression of CD200 in a series of MBCL and DLBCL cases.
Design: Cases of DLBCL and MBCL diagnosed between 2006-2011 were retrieved from archival files of our pathology department. A total of 106 cases of DLBCL and 11 cases of MBCL were used in our study. Diagnostic slides from all cases were reviewed and representative paraffin blocks were selected for preparation of tissue microarray (TMA). Immunohistochemical analysis using CD200 antibody was performed using paraffin sections from TMA. CD200 was considered to be positive in a case if more than 30% of the neoplastic cells expressed CD200 at a staining intensity of 2+ or more. The staining intensity was determined comparing it to the smaller B and T cells in the background which acted as an internal control.
Results: CD200 was expressed in (6/11) 54% of MBCL compared to 5% (5/106) of DLBCL. All MBCL cases were strongly positive (2+ and 3+ with >30% staining) for CD200 and showed a membranous staining. They also showed CD20 positivity in (6/6)) 100% cases but CD30 positivity in only (1/6) 17% cases. Clinically, 66% (4/6) cases had a higher stage disease at presentation. On the other hand, CD200 was only focally and weakly expressed in DLBCL. Interestingly all cases that express CD200 had a non-germinal center B-cell immunophenotype (CD10 negative, MUM-1 positive). Clinically, (4/5) 80% of the positive cases were associated with lower stage, no B symptoms and no bone marrow involvement.
Conclusions: CD200 is frequently expressed in MBCL but only rarely expressed in DLBCL cases and thus a useful marker to differentiate between Mediastinal large B-cell lymphomas and Diffuse large B-cell lymphomas. In DLBCL, expression of CD200 is limited to cases with non germinal center phenotype and may be a useful prognostic marker in this group of cases.
Category: Hematopathology

Monday, March 4, 2013 1:00 PM

Poster Session II # 213, Monday Afternoon


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