[903] The Immunohistochemical Profile of the Plasmacytoid Variant of Urothelial Carcinoma: A Study of 11 Cases

Chia-Sui Kao, Muhammed Idrees, Liang Cheng, David J Grignon. Indiana University, Indianapolis, IN

Background: Urothelial carcinomas (UC) exhibit many patterns, one of which is the plasmacytoid variant, characterized by discohesive tumor cells displaying a "plasmacytoid" appearance. Cells also frequently have a monocyte-like or signet ring cell-like morphology. The plasmacytoid variant is prone to misinterpretation as other neoplasms, especially in a limited sample, most commonly as plasmacytoma, metastatic lobular carcinoma of the breast or signet ring cell carcinoma of the gastrointestinal tract. Distinguishing plasmacytoid variant of urothelial carcinoma (PVUC) from other entities can be achieved using an appropriate panel of immunohistochemical stains. Furthermore, MUC protein expression has been the focus of studies on other aggressive variants of UC. The purpose of this study was to further define the IHC profile of PVUC including MUC protein expression.
Design: From our surgical pathology files, 11 cases of PVUC were identified and confirmed by reviewing hematoxylin and eosin stained sections. The plasmacytoid variant was defined by the presence of discohesive tumor cells with centrally or eccentrically located nuclei and moderate eosinophilic or amphophilic cytoplasm, infiltrating as single cells, cords or solid aggregates. Immunohistochemical stains were performed on all cases and evaluated for proportion and intensity of positivity.
Results: PVUC expressed p53 protein (100%), MUC1 (90%), 34ßE12 (80%), MUC4 (70%), CD138 (70%), CK20 (64%), CK7 (64%), p63 (55%), MUC5 (50%), MUC2 (40%), E-cadherin (30%), and uroplakin (27%). Progesterone receptor was positive in only one case (10%). MUM1, MUC6, CDX2, and estrogen receptor were uniformly negative.
Conclusions: PVUC can generally be recognized by careful morphologic evaluation. However, in a limited sample, the use of immunohistochemical stains may be necessary to make an accurate diagnosis. A panel including 34BE12, p53, MUC4/MUC5, MUM1, CDX2, and ER/PR can distinguish the tumor from mimics in most cases. MUC proteins, in particular MUC1 and MUC4, are frequently overexpressed. These transmembrane glycoproteins have been associated with aggressive tumor behavior in other sites, possibly through cell proliferation and apoptosis.
Category: Genitourinary (including renal tumors)

Tuesday, March 20, 2012 1:00 PM

Poster Session IV # 81, Tuesday Afternoon


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