[1427] CD123 and CD2AP Immunohistochemical Staining Shows Plasmacytoid Dendritic Cells Are Present in All Reactive Lymph Nodes but Their Numbers and Growth Pattern Vary Based on Pathologic Diagnosis

MA Rollins-Raval, SH Swerdlow, T Marafioti, CF Garcia. University of Pittsburgh School of Medicine, Pittsburgh, PA; John Radcliffe Hospital, Oxford, United Kingdom

Background: Plasmacytoid dendritic cells (pDCs) are known to be prominent in certain reactive conditions, including hyaline vascular variant Castleman disease (HVCD) and Kikiuchi lymphadenitis (KL), but their number and distribution in other reactive settings have not been extensively studied, especially using immunohistochemistry (IHC). pDCs can now be identified using CD123 and the newer more specific CD2AP IHC stains.
Design: IHC stains for CD123 and CD2AP were performed on reactive lymph nodes with HVCD(6), KL(1), autoimmune disease(7), sarcoidosis(3), granulomatous infections(7), viral infections (CMV, HIV, HCV) (8),cases consistent with toxoplasmosis (c/wT)(5) and dermatopathic lymphadenopathy (DL)(4).Cases were scored independently by 3 pathologists for the overall number of pDCs (1-4+) & pDC growth patterns: tight aggregates (TA),loose aggregates/cohesive clusters (LA/C) and scattered single cells (SSC)(0-4+).Discrepancies of ≤1 were averaged and others resolved by consensus.
Results: There is strong correlation between CD123 and CD2AP IHC for overall number of pDCs (r=0.92) & for TA, LA/C & SSC (r=0.87, 0.88 and 0.69, respectively). Results for CD123 and CD2AP were then averaged for further analyses. PDCs were present in all reactive conditions, being least numerous overall in DL, c/wT & viral infections.TA of pDCs were most frequently seen in HVCD (p<0.001,except DL and KL) followed by DL. pDCs were also prominent at the periphery of granulomas.

Conclusions: CD2AP correlates well with CD123 in evaluating pDCs in lymph nodes. PDCs are present in essentially all reactive lymph nodes; however, many are distributed in loose aggregates, clusters and singly, so they are not readily apparent in routine sections. PDC number and distribution vary based on the type of reactive lymph node with tight aggregates most commonly seen in hyaline vascular variant Castleman disease but with prominent pDCs also seen in other reactive settings.
Category: Hematopathology

Tuesday, March 23, 2010 9:30 AM

Poster Session III # 216, Tuesday Morning


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