[863] PAX Immunoreactivity Patterns in Anaplastic Wilms Tumors

Rong Fan. Indiana University, Indianapolis, IN

Background: PAX gene products belong to a family of nuclear transcription factors involving embryogenesis and many developmental controls such as kidney, eye, ear, nose, and brain. Though the patterns of expression in Wilms tumor were studied in the past, thitherto no study was designed to test the particular differential immuno expression patterns of PAX genes in unfavorable histology Wilms tumor (UH) and favorable histology Wilms tumor (FH). Towards this end this study was oriented and conducted.
Design: 26 cases of Wilms tumor were collected from our surgical pathology files from 2005-2010. 12 of the 26 cases were of unfavorable histology/anaplastic type. The remaining 14 cases were of favorable histology. Original H&E slides and immunostains for PAX2, PAX5, and PAX8 were reviewed. The intensity of nuclear staining was evaluated for each marker and was assigned an incremental score of 0, 1+, 2+, or 3+. The extent of staining was categorized as focal (<25%), multifocal (25% to 75%), or diffuse (>75%).
Results: All 14 cases of FH were diffusely and strongly positive for PAX2. There were 9 of 12 cases UH displayed variable immunoexpression for PAX2; 3 other cases were inconclusive. PAX8 immuno expression were noticed in 14 and 10 cases of FH and UH, respectively. All the positive staining involved both blastema and epithelial components. PAX5 showed reactivity in 3 cases of each FH and 2 case of UF. Most interestingly, PAX2 expression seems to be stronger in blastema component than in the epithelial component (Figure 1) and anaplasia foci do not seem to be staining with PAX2.




Conclusions: In all cases Pax2 and Pax8 genes appear to be expressing in both variants of Wilms tumor, but Pax5 gene expression appear to be all negative with rare exceptions. This study established that the PAX gene expression patterns in both Wilms tumor variants, favorable and unfavorable histology are similar but PAX 2 staining pattern has some unique features in unfavorable histology Wilms tumor.
Category: Genitourinary (including renal tumors)

Wednesday, March 6, 2013 1:00 PM

Poster Session VI # 159, Wednesday Afternoon

 

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