[1478] Increased CD5 Positive Polyclonal B-Cells in Castleman Disease, and Lymphoid Hyperplasia with Castleman-Like Features: A Diagnostic Pitfall

Qingyan Liu, Theresa Davies-Hill, Kourosh Pakzad, Mark Raffeld, Liqiang Xi, Stefania Pittaluga, Elaine S Jaffe. NCI/NIH, Bethesda, MD

Background: CD5 positive B-cells have been implied to play an important role in autoimmune disorders, such as rheumatoid arthritis and Sjogren syndrome. Castleman disease (CD) also has been associated with autoimmune disorders. Although CD5 expression on B cells of expanded mantle zones was reported in the plasma cell variant of CD, this finding has not been confirmed by others. We sought to determine if CD5-positive B-cells were expanded in reactive lesions, focusing on the hyaline vascular variant of CD (HV-CD) and lymphoid hyperplasias with Castleman-like features.
Design: 15 cases (11 HV-CD, 1 plasma cell variant of CD, and 2 lymphoid hyperplasia with Castleman-like features) collected from our hematopathology consult service from 2010-2011 were screened for CD5 expression on mantle zone B cells by immunohistochemical staining (IHC) using both a rabbit monoclonal anti-CD5 antibody (SP19)and mouse monoclonal anti-CD5 antibody (4C7). PCR analysis for immunoglobulin gene rearrangement was performed. Flow cytometry (FC) data was correlated with the morphologic findings when available.
Results: 6 of the 15 cases (4 HV-CD, 2 lymphoid hyperplasia with Castleman-like features) showed diffuse CD5 positivity on mantle zone B cells by the CD5/SP19 antibody, but not by the CD5/4C7 antibody. The median age of the CD5-positive cases was 46 yrs. with a female predominance (M:F=1:2), whereas the median age of the CD5-negative cases was 22 yrs. with a male to female ratio of 5:4. All cases were negative for Cyclin D1. Four cases with FC data showed the B cells to be polyclonal. All of the 5 cases tested were negative for clonal immunoglobulin gene rearrangement by PCR analysis.
Conclusions: Mantle zone B-cells positive for CD5 may be expanded in CD or lymphoid hyperplasia with Castleman-like features, and can be detected with newer, more sensitive reagents. Caution is warranted to avoid overdiagnosis of CD5positive B-cell lymphomas, which can sometimes have an in situ pattern of involvement, restricted to the mantle zones.
Category: Hematopathology

Monday, March 19, 2012 1:00 PM

Poster Session II # 230, Monday Afternoon

 

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