[946] Pathologic Characterization of Bosniak Type III Cystic Lesions of the Kidney

BP Portier, A Smith, E Remer, C Magi-Galluzzi, M Zhou. Cleveland Clinic Foundation, Cleveland, OH

Background: Renal cystic lesions are classified radiologically using the Bosniak classification system. Bosniak class III lesions are considered “indeterminate” and represent a grey area in which surgical removal of the cystic lesion is recommended even though some cystic lesions will ultimately be benign on pathologic examination. The incidence of malignant versus benign Bosniak class III lesions as determined by pathologic examination is not well documented. We investigated such incidence in a large series of patients with Bosniak class III lesions treated with nephrectomy.
Design: The Cleveland Clinics radiology database from 1/1999 to 9/2009 was reviewed. Selection criteria for inclusion in study included presence of renal cystic lesion classified as Bosniak class III. A total of 202 patients were identified with radiology confirmed Bosniak III lesions. Surgical pathology reports from these 202 patients were reviewed.
Results: Of the 202 patients with Bosniak class III cystic lesions, 115 (56.9%) underwent nephrectomy, 14 (6.9%) were biopsied, and 73 (36.1%) did not undergo resection or biopsy. Of the 115 nephrectomies, 39 (33.9%) were benign lesions [22 (19.1%) non-neoplastic cysts, 14 (12.2%) cystic nephroma/mixed epithelial stromal tumor, and 3 (2.6%) oncocytomas]. 76 (66.1%) were renal cell carcinomas (RCC) [43 (37.4%) clear cell RCC, 23 (20%) papillary RCC, 10 (8.7%) unclassified RCC, and 8 (7.0%) cases were multilocular cystic RCC]. Of the 70 RCCs with staging information, 44 (62.9%) were pT1a, 18 (25.7%) were pT1b, 5 (7.1%) were pT2, and 3 (4.3%) were pT3a.
Conclusions: In our study, a significant fraction (33.9%) of Bosniak class III cystic lesions were non-neoplastic. RCC represented 66.1% of the Bosniak III cystic lesions and the majority 88.6% were low stage (pT1a and 1b). This data indicates that the majority of lesions classified as Bosniak III cystic lesions represent either a non-malignant or low grade RCC. We are currently investigating radiologic characteristics of our Bosniak class III population that may aid in the distinction of benign cystic lesions from malignant.
Category: Genitourinary (including renal tumors)

Monday, March 22, 2010 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 134, Monday Morning

 

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