[892] A Subset of Invasive Urothelial Carcinomas of the Renal Pelvis Show Immunoreactivity with the Monoclonal Anti-PAX8 Antibody

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

Background: Positive staining with the polyclonal anti-PAX8 antibody has been shown in a subset of invasive urothelial carcinomas of renal pelvis origin. The expected immunoreactivity with polyclonal PAX8 in some tissues and neoplasms has now been shown to be due to cross reactivity. Immunoreactivity with the new monoclonal anti-PAX8 antibody has not been evaluated in upper tract urothelial carcinoma. Knowledge of the PAX8 immunoreactivity pattern in upper tract urothelial carcinomas is important in the diagnostic distinction from renal cell carcinoma, especially since small image guided biopsies are now commonly used to guide definitive clinical management.
Design: We identified invasive urothelial carcinomas of the renal pelvis with available H&E glass slides and paraffin blocks from our surgical pathology archives. All slides were reviewed to confirm diagnoses and a representative slide was stained with polyclonal anti-PAX8 (1:20 dilution, Proteintech, Chicago, IL) and monoclonal anti-PAX8 (1:50 dilution, clone BC12, BioCare, Concord, CA) antibodies using standard citrate retrieval techniques. Immunoreactivity was scored as positive if any nuclear staining was present in the invasive component and the total percentage of neoplastic cells with positive staining was recorded.
Results: Four of 20 invasive urothelial carcinomas of the renal pelvis (20%) had nuclear staining with a polyclonal anti-PAX8 antibody [80%, 80%, 50%, and 20% of neoplastic cells]. The same four renal pelvis tumors also demonstrated immunoreactivity with a monoclonal anti-PAX8 antibody; however, there was both a lower percentage and intensity of staining [<5%, 10%, 20%, and <5% respectively of neoplastic cells]. Both antibodies displayed a heterogeneous patchy immunoreactivity pattern throughout the sections.
Conclusions: In this study, polyclonal and monoclonal anti-PAX8 immunoreactivity was seen in the same 20% of invasive urothelial carcinomas of renal pelvis origin. While the monoclonal anti-PAX8 antibody reacted with fewer neoplastic cells and demonstrated less intense staining, both antibodies displayed a heterogeneous pattern of immunoreactivity with areas of stronger staining present. Knowledge of this potential immunoreactivity pattern is important when faced with the diagnostic distinction of renal cell carcinoma from invasive urothelial carcinoma on needle biopsy.
Category: Genitourinary (including renal tumors)

Tuesday, March 20, 2012 1:00 PM

Poster Session IV # 99, Tuesday Afternoon


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