[840] Invasive Urothelial Carcinomas of the Renal Pelvis Show Immunohistochemical Expression for PAX8 and PAX2 in a Subset of Cases.

Jonathan Hughes, Ankur R Sangoi, Jesse K McKenney. Stanford, Stanford, CA; El Camino Hospital, Mountain View, CA

Background: Previous studies have reported discrepant staining results with anti-PAX antibodies in invasive urothelial carcinomas of the upper urinary tract. Knowledge of the PAX immunoreactivity pattern in these urothelial tumors is particularly important for the differential diagnostic distinction from renal cell carcinoma in small image guided biopsies, which is critical to the subsequent planning of clinical management.
Design: We identified invasive urothelial carcinomas of the upper urinary tract (i.e. ureter and renal pelvis primaries) with available H&E stained glass slides and paraffin blocks from our surgical pathology archives. All slides were reviewed to confirm diagnoses and a representative slide was stained with anti-PAX8 (polyclonal, 1:20, Proteintech, Chicago, IL) and anti-PAX2 (Z-RX2, 1:100, Zymed, San Francisco, CA) antibodies using standard citrate retrieval techniques. Immunohistochemical expression was scored as positive if any nuclear staining was present and the percentage of neoplastic cells with positive staining was recorded.
Results: 30 total invasive urothelial carcinomas of the upper tract were identified (10 ureter and 20 renal pelvis primaries). Four of 20 invasive urothelial carcinomas of the renal pelvis (15%) had nuclear staining with anti-PAX antibodies [1 PAX8+/PAX2- (80% of neoplastic cells); 1 PAX8+/PAX2- (50% of neoplastic cells); 1 PAX8+/PAX2+ (20 and 15% of neoplastic cells, respectively); 1 PAX8-/PAX2+ (5% of neoplastic cells)]. Nuclear immunoreactivity for PAX2 was generally weaker than PAX8 and had higher cytoplasmic background staining. None of the 10 invasive urothelial carcinomas of the ureter expressed PAX-8 or PAX-2.
Conclusions: In this study, PAX8 was expressed in 15% and PAX2 in 10% of primary invasive urothelial carcinomas of the renal pelvis by immunohistochemistry, but the ureteral primary tumors were negative. This potential staining should be considered when facing the differential diagnostic distinction of renal cell carcinoma from invasive urothelial carcinoma of the renal pelvis, particularly in small image guided biopsy samples where the histologic appearance may be distorted.
Category: Genitourinary (including renal tumors)

Wednesday, March 2, 2011 9:30 AM

Poster Session V # 111, Wednesday Morning


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