[1220] Can CD123 Immunohistochemical Stain for Plasmacytoid Dendritic Cells Be Used as an Adjunctive Diagnostic Marker in Marginal Zone Lymphomas at Different Sites?

Rashmi Batra, Violette Ghali. St Luke's Roosevelt Hospital Center and Beth Medical Center, New York

Background: Plasmacytoid dendritic cells (PDC) are a subset of dendritic cells, found in blood and lymphoid tissue. They recognize viral and bacterial antigens, produce Type I interferons, activate T cells and play a role in initiation of immune response. They consistently express CD123 (IL-3 receptor), CD68, CD4 and a subset of CD56. CD123 positivity is proven in primary cutaneous marginal zone lymphoma where clusters of CD123+ PDC were found in close proximity to monoclonal plasma cells and T cells in high numbers. (Am J Surg Pathol 2009; 33:1307-1313).
Design: The aim of this study was to see if CD123 IHC can be used as an adjunctive diagnostic marker in marginal zone lymphomas (MZL) at other different sites and compare it with that of already published distribution in cutaneous marginal zone lymphomas. We did a retrospective study of 32 cases of MZL diagnosed at our institution between 01/01/2000 to 03/31/2010.The diagnosis was based in all cases by morphology, IHC and confirmed by flow cytometry. Clonality was demonstrated in all cases. A case of Kikuchi's lymphadenitis with CD123+ cell clusters was used as a control. IHC stains were performed on MZL lung (n=3), small bowel (n=1), gastric (n=2), brain (n=1), primary nodal MZL (n=7), splenic MZL (n=3), breast (n=1), salivary gland (n=2), soft tissue (n=4), cutaneous (n=2), orbit (n=4) and bone marrow (n=2).Cases were scored for PDC's as loose clusters:5-10 cells/HPF, tight clusters: 5-10 cells /HPF, single scattered cells and negative.
Results: 19/32 (59.3%) cases were negative, with internal positive control. 5/32 cases (15.6%) were positive with 5-10 cells in a perivascular distribution with both tight and loose clusters and scattered single cells. Interestingly, we noticed strong positivity in histiocytes in 1 lung case which was not used for scoring. Positive cases included 2 salivary gland, 1 lymph node, 1cutaneous/forearm mass and 1orbital lesion. 8/32 cases (25.0%) showed single scattered occasional positive cells.
Conclusions: This study did not prove that IHC for CD123 could be used as an adjunctive diagnostic marker in MZL. Interestingly out of our 2 cutaneous lesions, 1 was positive and the other was negative. 2/2 of gastric and 3/4 of our orbit cases were negative, where a role of T cell mediated immune response to an infectious agent has been clearly established. At this point we do not know the relevance of the positive cases (15.6% of the total cases) in our study, raising questions about the utility of this marker in diagnosis of MZL.
Category: Hematopathology

Wednesday, March 2, 2011 1:00 PM

Poster Session VI # 201, Wednesday Afternoon


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