[1356] Utility of D2-40 Expression and the Microenvironment in Distinguishing Inflammatory Pseudotumors (IPT) from Follicular Dendritic Cell (FDC) Tumors of Lymph Node (LN) and Spleen: Clinicopathologic Comparison of 6 Cases

M Jamali, DJ Bailey. University Health Network, Toronto, ON, Canada

Background: IPTs of LN and spleen represent a very rare, biologically distinct entity compared to IPTs in soft tissue. These tumors are often diagnostic dilemmas as they show morphologic heterogeneity and can bear striking clinicopathologic similarities to FDC sarcomas (FDCS) of LN and spleen. This creates an even greater challenge with potential prognostic implications for a reliable diagnosis of FDCSs with IPT features and IPTs expressing FDC markers. Studying the clinicopathologic nuances of these tumors especially with respect to D2-40 patterns and microenvironment may help the hematopathologist faced with such rarities.
Design: Cases of IPT and FDCS of LN and spleen (1990 to 2009) were retrieved from our institution's archives. H&E and immunohistochemical stains for CD3,CD20,CD21,CD68,CD138,CD1a,ALK protein, S100,keratins, actins, EBV and D2-40 were performed and reviewed.
Results: Four and 2 cases of IPT and FDCS, respectively, were identified (3M:3F;39-65yrs, mean 55.3yrs). Four arose in LNs (2 axillary;1 neck;1 abdominal) and 2 in spleen.Of the IPTs, 2 LNs and 2 spleens showed 1 to multiple nodular spindle cell proliferations with focal storiform pattern and areas of hyaline fibrosis.The nodules contained variable proportions of chronic inflammatory cell infiltrate consisting of small lymphocytes, plasma cells and histiocytes/giant cells.Of the FDCS, 2 LNs showed near complete replacement by a spindle cell proliferation arranged in sheets, short fascicles and whorls with minimal mitoses and light,intimate infiltration by chronic inflammatory cells.Of these, one lacked significant nuclear pleomorphism.No necrosis was seen in any case. All tumor cells were negative for S100, CD1a, ALK and keratins.EBV was positive in one case of IPT spleen.Nodules in IPT LNs and spleens showed prominent but highly variable CD3, CD20, CD138 and CD68 expression, as did the one case of FDCS with little atypia. Both cases of FDCS nodules stained focally for CD21 with no staining in the rest.D2-40 expression was strong and predominantly localized to the membrane in IPTs and cytoplasm in one FDCS.The second case of FDCS showed both weak membranous and cytoplasmic staining.
Conclusions: Morphologic and immunohistochemical expression patterns of D2-40,FDC markers as well as proportion and type of inflammation in concert can aid in the reliable diagnosis of IPTs of LN and spleen as part of a biological spectrum ranging from conventional IPT to FDCS with IPT-like features.
Category: Hematopathology

Tuesday, March 23, 2010 9:30 AM

Poster Session III # 215, Tuesday Morning


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