[755] Evaluation of Renal Tumors by Image Guided Biopsies with an Emphasis on Oncocytic Neoplasms: A Retrospective Four Year Study from a Large Academic Institution.

Ritu Bhalla, Angela Wu, Lakshmi P Kunju. University of Michigan Medical Center, Ann Arbor

Background: Image guided needle core biopsies of renal masses (IGRB) are becoming increasingly common. We evaluated the adequacy, accuracy and limitations of IGRB in the management of patients with renal tumors in a high volume academic institution.
Design: The database was searched for all IGRB performed between 2006 and 2009 at our institution.
Results: Three hundred and seventy one IGRB in adults (age range 22-92 yrs, mean 62 yrs, M:F 1.4 ) were identified. IGRBs were sufficient for diagnosis in 329 (88.6%) patients. Biopsies were categorized as: 180 (48%) clear cell RCC; 47 (13%) tubulo-papillary RCC; 56 (15%) oncocytic neoplasms (ON){40 (11%) oncocytomas, 5 (1%) chromophobe RCC, and 11 (3%) ONs which could not be definitively classified}; 7 (2%) urothelial carcinomas; 19 (5%) benign/inflammatory; 20 (6%) miscellaneous {4 metastases, 4 high grade RCC, 4 Ewing sarcoma, 4 RCC with clear/papillary features, 2 sarcomas, 1 high grade carcinoma, unclassifiable, and 1 lymphoma}. Immunohistochemistry was performed in 90 (24%) cases. In the the majority (89%) of the ONs immunohistochemistry was performed, including CK7 (50 cases), vimentin (14), PAX-2 (6), c-kit (5), and RCC Ag (1). Of the 11 ONs which could not be classified, the diagnoses most often rendered was oncocytoma vs chromophobe RCC (5/11) and oncocytoma vs.other RCC (6/11). Followup was available in 51/56 ONs. Twenty four (42%) ONs (20 oncocytomas, 1 chromophobe, 3 unclassifiable) were followed up radiologically, 18 (32%) {13 oncocytomas, 2 chromophobes, 3 unclassifiable} underwent radiofrequency ablation, and 9 (16%) {2 oncocytomas, 2 chromophobes, 5 unclassifiable} underwent excision. The biopsy diagnosis was confirmed on excision in 3 cases. In one case, the biopsy diagnosis of oncocytoma was changed to chromophobe RCC on excision. Of the 5 ON which could not be classified on biopsy, the diagnoses on excision were chromophobe RCC (2), tubulocystic RCC (1), papillary RCC (1) and oncocytoma (1).
Conclusions: Image guided renal mass biopsies are generally adequate, and a definitive diagnosis can be established in the majority of cases. ONs provide the biggest diagnostic challenges; however, with the aid of immunohistochemistry, the majority (80%) could be still be definitively classified as either oncocytoma or chromophobe RCC. On excision, the ONs which cannot be classified are usually diagnosed as a variety of RCC.
Category: Genitourinary (including renal tumors)

Monday, February 28, 2011 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 108, Monday Morning


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