[810] Worrisome Histologic Features in Benign Renal Oncocytoma: Immunohistochemical and Cytogenetic Analysis

Matteo Brunelli, Miriam Ficial, Diego Segala, Enrico Munari, Serena Pedron, Stefano Gobbo, Marco Chilosi, Asli Yilmaz, Kiril Trpkov, Brett Delahunt, John N Eble, Liang Cheng, Guido Martignoni. University of Verona, Verona, Italy; University of Calgary, Calgary, AB, Canada; University of Otago, Wellington, New Zealand; Indiana University, Indianapolis, IN

Background: Renal oncocytoma is a benign renal cell neoplasm that accounts for about 7% of kidney tumors. It sometimes shows atypical histological features (macroscopic central scar including worrisome cells with either clear cell changes or basophilic type 1 papillary renal cell carcinoma-like appearance, cytological atypia, oncoblasts, necrosis, perirenal fat infiltration, vascular invasion) which can represent a potential source of misdiagnosis of malignancies. The aim of the study is to characterize the immunophenotypical and cytogenetic profile of renal oncocytomas with atypical features.
Design: Seventy-six renal oncocytomas were retrieved from the Pathology database, University of Verona. Revision of the whole histological slides was performed, with morphological identification of atypical features. Ten cases representative of the group of worrisome histologic features were selected for immunophenotypical and cytogenetic analyses. Immunohistochemistry was performed using antibodies against Parvalbumin, CD10, CD13, Vimentin, Cytocheratin 7 (CK7), Racemase and S100A1. Fluorescence In Situ Hybridization (FISH) was used to detect chromosome 1, 2, 6, 7, 10, 17, Y and 11q13 abnormalities in “classical” and worrisome patterns.
Results: Tumors with at least one atypical morphological pattern were 48,7%. Central fibrous scar including epithelial cell proliferations was the most common atypical feature and was present in the 26,3%, cytological atypia in 15,8%, oncoblasts in 10,5%, vascular invasion in 9,2% and perinephric fat extension 2,6% of the cases. Mitosis were present in 1,3% of cases whereas no necrosis was found. Cell proliferations in the context of central fibrous scar had an immunophenotype similar to that observed in papillary renal cell carcinoma (CK7, CD10, CD13 and Racemase expression), but the entire chromosomal profile tested showed numerical normal pattern. All other atypical morphological features had a disomic chromosomal profile, with the exception of the areas of cytological atypia, that demonstrated frequent trisomies (67% of cases).
Conclusions: Immunohistochemistry and cytogenetic investigations could be a useful tool in differential diagnosis between benign renal oncocytoma with atypical features and malignant epithelial tumors of the kidney, especially when the diagnosis should be done on limited material.
Category: Genitourinary (including renal tumors)

Tuesday, March 20, 2012 9:30 AM

Poster Session III # 159, Tuesday Morning


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