IMAGING

Evaluation of sonographically guided percutaneous core biopsy of renal masses
Caoili EM, Bude RO, Higgins EJ, Hoff DL, Nghiem HV
Department of Radiology, University of Michigan Medical Center, Ann Arbor, MI, USA
AJR Am J Roentgenol. 2002; 179:373-8

• Purpose: Our objective was to determine the utility of sonographically guided percutaneous core biopsy to evaluate renal masses.
• Material and Methods: We conducted a retrospective analysis of our imaging-guided procedures from January 1999 to June 2001. We performed 26 sonographically guided percutaneous core biopsies of renal masses in 26 patients. From two to five specimens were obtained from a single mass in each patient using an 18-gauge automated biopsy system. We examined the patients’ medical records, pathology results, and imaging studies. Core biopsy results were compared with surgical pathology (n=6) or clinical follow-up (n=20).
• Results: All biopsies provided sufficient material for analysis. Biopsy findings were positive for malignancy in 19 (73%) of 26 masses. Histologic diagnoses included renal cell carcinoma were (n=11), metastasis (n=3), lymphoma (n=2), and transitional cell carcinoma (n=2). Specific cell type characterization could not be made on one biopsy, but the specimens were highly suspicious for malignancy. Biopsy revealed seven (27%) of 26 benign diagnoses: oncocytoma (n=3), angiomyolipoma (n=2), and fibrosis (n=2). The average follow-up period for patients with benign diagnoses was 10 months. One case of surgically proven necrotic pyelonephritis was mischaracterized as fibrosis at core biopsy. Sonographically guided percutaneous core biopsy of renal masses showed a sensitivity of 100% and a specificity of 100% for the diagnosis of malignancy. The core specimens yielded a specific diagnosis in 92% (24/26) of masses. No immediate complications occurred after the procedure. One patient developed a pseudoaneurysm that presented 3 months after the biopsy.
• Conclusion: Sonographically guided percutaneous core biopsy is a reliable and accurate method for evaluating renal masses.
  
  
• Editorial Comment
  The use of percutaneous biopsy of a renal mass has a limited role in the current era of high-quality imaging procedures. The majority of renal masses are treated based on imaging tests (Ultrasound with power Doppler, Helical – CT, and Magnetic Resonance Imaging). By the use of strict radiologic criteria, and the indispensable correlation with clinical and laboratorial data, we can achieve a very high overall accuracy in distinguishing benign versus malignant disease. Although recently described as a useful procedure(1), fine-needle aspiration biopsies are not used routinely. This can be explained by its low sensitivity for detection of malignancy, and undesirable false-negative rates. This method, however, can occasionally be used for cytologic confirmation of an infected cyst or abscess. On the contrary, core biopsy of renal mass is a safe and accurate procedure that may be used in some special clinical and radiologic situations. The authors presented a retrospective review of the utilization of percutaneous ultrasound-guided renal biopsy in 26 patients. From each mass a mean of 3 cores was obtained, and although post biopsies radiologic imaging was not performed in all patients, small perinephric hematoma (1-3 cm) was observed in 19% of patients. One patient developed a pseudoaneurysm with gross hematuria, and a perinephric hematoma requiring arterial embolization. Among these 29 patients, 9 had a known extrarenal neoplasm; 4 had multiple renal masses, 2 had adrenal masses, 2 had suspected renal masses, but were not considered surgical candidates. As we can see by their results, core biopsy of renal masses has few indications, and is used routinely mainly for identifying lymphoma or metastasis from a non-renal primary tumor; this can be confirmed, since only 5 of 26 patients(19%) presented an indeterminate renal mass. The main value of this publication is to show that percutaneous renal biopsy guided by ultrasound is better than when guided by CT (2). Unlike CT, ultrasound allows continuous visualization of the needle as it enters the mass, with much better accuracy (95%). CT-guided biopsy has the drawbacks of occasional movement of the needle when it is manipulated outside the gantry, and the possibility of displacing the mass instead of puncturing it.

References
1. Herts, BR: Imaging guided biopsies of renal masses. Curr Opin Urol. 2000; 10:105-9.
2. Lechevallier E, Andre M, Barriol D, Daniel L, Eghazarian C, De Fromont M et al.: Fine-needle percutaneous biopsy of renal masses with helical-CT guidance. Radiology 2000; 216:506-10.

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