[742] Epithelial p16 Expression Is Associated with Chromophobe Renal Cell Carcinomas but Not Oncocytic Renal Lesions.

Vijayalakshmi Ananthanarayanan, Maria Tretiakova, Jerome Taxy, Tatjana Antic. University of Chicago, IL

Background: p16 protein expression by immunohistochemistry (IHC) is commonly used as a surrogate marker for human papilloma virus (HPV) infection in the cervix. Given the histologic similarity between viropathic koilocytes and nuclear changes of chromophobe renal carcinomas (CHRCC), we sought to analyze p16 expression in CHRCC, to evaluate its role in carcinogenesis. Additionally, we assessed the diagnostic utility of this marker to distinguish CHRCC from renal oncocytoma/oncocytosis (ONC), a close differential diagnoses.
Design: Tissue microarrays (TMAs) were constructed using 1 mm triplicate cores from 43 CHRCC and 24 ONC cases. Normal kidney tissues were included as controls. TMAs were immunostained for p16 using a mouse monoclonal antibody (Biocare, 1:400 dilution). Spots were evaluated in a blinded fashion to estimate the percentage of staining in the vascular, epithelial nuclear (EN) and epithelial cytoplasmic/membranous compartments (ECM).
Results: Normal kidney was devoid of p16 staining within any of the compartments. CHRCC was significantly associated with any epithelial nuclear p16 expression (8/43 cases) vs. ONC (0/24 cases) [Fisher exact p=0.043]. A greater proportion of CHRCC (12/43 cases) showed epithelial cytoplasmic staining when compared to ONC (2/24 cases) [Fisher exact p=0.069]. Variable endothelial staining was noted in a subset of both CHRCC and ONC. As shown in Table. 1, no difference was observed in percent staining for vascular and ECM compartments between the two groups.

Table 1. Percent staining in ONC and CHRCC across various histologic compartments
Histologic CompartmentONCCHRCCp-value
 Average % Staining (n)Average % Staining (n) 
Vascular24.43 (09)25.37 (11)0.92
Tumor ECM6.25 (02)25.05 (12)0.36
Tumor ENNo staining28.70 


Furthermore, there was no correlation between the p16 staining and pT stage in CHRCC.
Conclusions: Epithelial p16 expression is more frequent in CHRCC than ONC. However, no association was observed between pT stage and p16 staining. Vascular p16 staining, albeit a novel finding, was not statistically different between CHRCC and ONC. Epithelial p16 expression in a significant subset of CHRCC suggests a possible role of HPV that merits further investigation.
Category: Genitourinary (including renal tumors)

Wednesday, March 2, 2011 9:30 AM

Poster Session V # 93, Wednesday Morning

 

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