[1475] Immunohistochemical Characterization of Vascular and Stromal Proliferations of Spleen

Dennis P O'Malley, Young S Kim, Aliyah Sohani, Lawrence Weiss, Sherrie Perkins, Jerome S Burke, Cyril Fisher, Attilio Orazi. Clarient Inc./GE Healthcare, Aliso Viejo, CA; City of Hope National Medical Center, Duarte, CA; Massachusetts General Hospital, Boston, MA; University of Utah, Salt Lake City, UT; Alta Bates Medical Center, Berkeley, CA; Royal Marsden Hospital, London, England, United Kingdom; Weill-Cornell Medical College, New York, NY

Background: Splenic vascular and stromal tumors are rare. Their ontogeny and classification are based on histologic evaluation and limited panels of immunohistochemical stains. Many of these disorders have overlapping features, which may understate significant differences in prognosis and recurrence risk. We evaluated a large number of rare stromal and vascular tumors using an extensive panel of immunohistochemical stains to characterize differences and similarities in their phenotype and cellular composition. We suggest underlying similarities and differences in current classification of these proliferations.
Design: 29 splenic proliferations were evaluated and compared to the stromal and vascular composition of 12 normal spleens. These included 15 vascular lesions (hemangioma=2, cord capillary hemangioma=7, SANT=4, littoral cell angioma=1, peliosis=1, angiosarcoma=1), 5 stromal disorders (infarct=3, fibrocongestive splenomegaly=3), 5 “inflammatory pseudotumors” and related entities, and 4 hamartomas and variants. Immunohistochemical panels included the following stains: LMO2, FLI1, WT1, CD34, CD8, CD31, CD21, CD163, CD68, SMA, IgG, IgG4 and Ki-67. An additional 31 samples were evaluated by LMO2.
Results: Pertinent results include the expression of WT1, FLI1 and LMO2 markers in splenic vascular lesions, which have not been previously reported in comparable numbers of cases. Specific staining for WT1 appears to identify vascular proliferation in these lesions. A subset of vascular and stromal proliferations in spleen associated with increased IgG4 positive plasma cells, suggesting possible differences in etiology of some lesions.
Conclusions: Because of their rarity, vascular and stromal proliferations of the spleen are challenging. Some of the “secrets” of these lesions can be overcome by thorough evaluation by immunohistochemical studies in larger series to uncover differences based on recently available stains. These findings may clarify some diagnostic difficulties and raise new question about the derivation and nature of some of these proliferations.
Category: Hematopathology

Tuesday, March 5, 2013 9:30 AM

Poster Session III # 181, Tuesday Morning


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