[1023] Expression of PAX8 in Non-Invasive Urothelial Carcinoma of the Bladder

Joseph M Sanfrancesco, Cristina Magi-Galluzzi, Donna Hansel. Cleveland Clinic Foundation, Cleveland, OH

Background: Pax8, one of nine members of the paired box gene family, is a transcription factor expressed in embryonic and normal adult tissues. This gene family is responsible for development of multiple organ systems by maintaining a progenitor state while preventing terminal differentiation. More recently, the expression of Pax8 in selected neoplasms, particularly thyroid and kidney, has been explored, although information in other tumor types is somewhat limited. We examined the expression pattern of Pax8 as a diagnostic marker in non-invasive papillary urothelial carcinoma (UCa), which has not been previously evaluated in detail.
Design: Using a laboratory database search system, 80 cases of non-invasive UCa from 2005 to 2012 were compiled, including low-grade (n=41) and high-grade (n=39) disease. Follow-up for each patient was obtained to ensure that no progression to invasive carcinoma had occurred at the time of this study. Immunohistochemical (IHC) staining with Pax8 was performed on constructed tissue microarrays. Interpretation of staining was completed using a 0-3 scale, with most prominent expression, based on intensity, being classified at 3 and no expression being classified as 0. IHC staining ≥ 2 was considered to be a positive result.
Results: High levels of Pax8 (≥ 2 staining) were identified in 68.2% (28/41) of low-grade and 61.5% (24/39) of high-grade non-invasive UCa cases. The positive staining pattern was similar in distribution for both high- and low-grade UCa cases. More intense staining was appreciated in the superficial portion of the epithelium, but positivity was diffuse in a majority of neoplastic cells.
Conclusions: Pax8 has been shown to be a sensitive and specific IHC marker in renal cell carcinoma. Based on our study, it is evident that Pax8 appears to be expressed in the majority of non-invasive, low-grade and high-grade papillary UCa of the bladder, suggesting a conserved role in the development and/or maintenance of non-invasive papillary lesions at this site. Further studies that evaluate the functional role of this transcription factor in bladder cancer are warranted.
Category: Genitourinary (including renal tumors)

Wednesday, March 6, 2013 1:00 PM

Poster Session VI # 167, Wednesday Afternoon


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