IMAGING

Incidence of malignancy in complex cystic renal masses (Bosniak category III): should imaging-guided biopsy precede surgery?
Harisinghani MG (1), Maher MM (1), Gervais DA (1), McGovern F (2), Hahn P (1), Jhaveri K (3), Varghese J (1), Mueller PR (1)
Division of Abdominal Imaging and Intervention(1) and Department of Urology (2), Massachusetts General Hospital, Boston, MA ,USA; Department of Medical Imaging (3), University Health Network-Mount Sinai Hospital, University of Toronto, Canada
AJR Am J Roent. 2003; 180:755-8

• Purpose: Complex indeterminate renal cystic masses (Bosniak type III) can have benign and malignant causes and have been traditionally considered surgical lesions. We sought to determine the incidence of malignancy and to assess a possible role for imaging-guided biopsy for this category of renal masses.
• Materials and Methods: Three hundred ninety-seven renal biopsies were performed at our institution between 1991 and 2000. Between January 1997 and August 2000, 28 Bosniak category III lesions, based on established CT imaging criteria on helical CT scans, were identified for analysis. The incidence of malignancy, based on surgical pathology or imaging follow-up and percentage of lesions proceeding to surgery, among these 28 lesions, was determined. The surgical results were correlated with the biopsy findings.
• Results: Of the 28 biopsied category III lesions, 17 (60.7%) were malignant (16 renal cell carcinomas and one lymphoma), and 11 (39.3%) were benign (six hemorrhagic cysts, three inflammatory cysts, one metanephric adenoma, and one cystic oncocytoma). Seventeen of the 28 lesions (16 renal cell carcinomas and one inflammatory cyst) had surgical resection after the biopsy. All resected lesions had pathologic diagnoses identical to the percutaneous imaging-guided biopsy results. The remaining 11 patients who had undergone nonsurgical biopsies had radiologic follow-up for a minimum of 1 year, with benign lesions showing no interval change.
• Conclusions: Renal biopsy and radiologic follow-up were useful in identifying nonmalignant lesions in complex cystic renal masses and avoided unnecessary surgery in 39% of patients.
  
• Editorial Comment
  Bosniak category III cystic masses are lesions which presents suggestive but not definitive signs of malignancy. For this reason they are designated as renal mass of indeterminate origin. The typical category III cystic mass shows thickened and irregular calcifications, uniform wall thickening, and thickened and irregular or multiple septa (>1 mm). It is well known that there is too much interobserver variability to distinguishing Bosniak II from Bosniak III cystic masses. Complementary evaluation with magnetic resonance imaging may be useful in some of these cases. Because there is 50-60% of chance of malignancy , the recommended treatment for Bosniak category III lesions is surgical resection( tumor enucleation, partial or total nephrectomy). Although imaging guided renal biopsy was performed for a different purpose (previous diagnosis for RF ablation), this study is useful to emphasize that if a percutaneous biopsy of a complex renal cyst should be done, it should be guided by CT and a 18 gauge needle should be used in order to obtain sufficient number of good quality cores. Fine-needle aspiration biopsy for cytology has too many false negative results. Some points are important when we are dealing with the management of a Bosniak category III renal cystic mass. First the patient’s clinical factors such as age and the presence or not of intercurrent illness can interfere in the choice of the treatment modality. Second, if surgery should be done, whenever is possible a conservative procedure should be performed. Third, close follow-up or percutaneous CT-guided biopsy are both valid procedures and should be used accordingly.

Dr. Adilson Prando
Department of Radiology
Vera Cruz Hospital
Campinas, São Paulo, Brazil