[802] Clear or Basophilic Type 1 Papillary Renal Cell Carcinoma-Like Cells Occurring in the Central Fibrous Scar of Renal Oncocytoma Represent a Potential Diagnostic Pitfall

M Brunelli, S Gobbo, D Segala, F Bonetti, S Bersani, F Menestrina, M Chilosi, K Trpkov, G Martignoni. University of Verona, Verona, Italy; University of Calgary, Calgary, Canada

Background: A subset of renal oncocytoma shows a macroscopic central scar, in which isolated or clusters of worrisome tumor cells with either clear cell changes or basophilic type 1 papillary renal cell carcinoma-like appearance can be observed. We investigated these abnormalities that may represent a diagnostic pitfall.
Design: Immunohistochemical expression of CD10, vimentin, CK7, racemase, GLUT-1 and S100A1 were scored in 20 renal oncocytomas (6 with a central fibrous scar, six, two and six with respectively a solid, tubulocystic and archipelagic pattern). Chromogenic in situ hybridization (CISH) was used to detect chromosome 7 and 17 abnormalities on both neoplastic and normal renal tissue.
Results: The tumour cells with clear cell or basophilic type 1 papillary renal cell carcinoma-like changes present in the renal oncocytomas with central scar displayed strong immunoexpression for CK7, vimentin and GLUT-1 in all 6/6 and racemase in 4 out of 6 cases. CD10 was revealed in 2/6 and S100A1 in 1/6 cases. All the 14 other renal oncocytomas and the peripheral oncocytic component out of the scar of the 6 aforementioned renal oncoytomas did not show vimentin and GLUT-1 immunoexpression; CD10 was focally (10% of neoplastic cells) observed in 5/14 whereas CK7 was focally present in 6/14 cases. One renal oncocytoma was positive for racemase. CISH revalead two signals in the normal renal parenchyma and in majority of neoplastic oncocytic, clear and basophilic type 1 papillary renal cell carcinoma-like cells (mean 55%).
Conclusions: 1) tumor cells found in the central fibrous scar of renal oncocytoma show atypical morphological such as clear or basophilic type 1 papillary renal cell carcinoma-like cells and immunohistochemical strong CK7, vimentin, GLUT-1 and racemase features in comparison with the oncocytic peripheral areas of the tumours; 2) the CK7 and racemase positive basophilic type 1 papillary renal cell carcinoma-like cells are lacking the trisomies of chromosome 7 and 17 which are the cytogenetic hallmark of the papillary renal cell neoplasms; 3) these findings represent a potential diagnostic pitfall and harbor clinical significance because immunostains may often used in differential diagnosis of renal tumors on limited biopsy specimens.
Category: Genitourinary (including renal tumors)

Tuesday, March 23, 2010 9:30 AM

Poster Session III # 136, Tuesday Morning

 

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