Introduction

1. Diagnostic Yield of 58 Consecutive Imaging-Guided Biopsies of Solid Renal Masses: Should We Biopsy All That Are Indeterminate?AJR 2007 MarchDepartment of Radiology and Pathology, Rhode Island Hospital

2. Introduction • Before the advent of CT and sonography, most renal masses were detected because patients presented with abdominal pain, hematuria, or symptoms of metastatic disease • Approximately 48% of renal tumors are detected incidentally by cross-sectional imaging

3. Traditionally, renal mass was treated by nephrectomy without a biopsy • A certain percentage of nephrectomies were performed for benign disease • A recent study: 376/2770(12.8%) of the masses removed were benign • For tumors < 1cm, it is 46.3% • 37% of solid renal masses received imaging-guided tumor ablation were benign lesions

4. Small renal mass was difficult to diagnosis by imaging alone • Because of the increasing number of incidentally discovered renal masses detected on cross-sectional imaging, it would be useful to accurately characterize them as benign or malignant to avoid unnecessary interventional therapy for benign lesions.

5. Material and Methods • Retrospectively reviewed all percutaneous renal mass biopsies performed during May 1998 to March 2005 at their institution • Inclusion criteria: renal mass • 59 renal mass biopsies were performed during this time and 1 was excluded because it is cystic and no contrast enhancement • Greatest diameter of mass was determined by imaging, biopsy reports. • Biopsy needle, gauge, technique, number of passes , and complications were also recoreded. • Pathology reports and biopsies were reviewed

6. CT guided biopsy: 55(95%) Sonographically guided biopsy: 3 • CT guidance were done on a single detector helical CT scanner with 1 to 5 passes • Sonographically biopsy were performed with 1 to 4 passes • 44 biopsies were performed using coaxial technique with 18- to 20- gauge side-cutting automated biopsy needles. • 14 biopsies using 20-gauge Franseen needle with a tandem technique

7. Biopsy results were defined as adequate if sufficient tissue was present according to the pathology report. • Adequate but nondiagnostic : normal renal parenchyma was obtained; predominantly necrotic material was obtained; visualized cells were obscured by blood, inflammation, or artifact.. • Tumor histology was classified according to the WHO 2004 classification

8. All specimens were prepared with H and E staining • Immunohistochemical staining was used if no definitive diagnosis was made by H and E staining • Statistical analysis was performed using Fisher’s exact test between needle type or gauge and diagnostic yield

9. Result • 48 patients have a enhancing renal mass on CT - 33 in their institutuion: HU > 15 - 15 from outside institution • 6 masses have enhancement on MRI • 4 patients have completely solid mass with no cystic features on sonography

10. 47 (81%) biopsies were performed just before percutaneous radiofrequency or microwave ablation • 11 biopsies were performed to determine the cause of mass for subsequent therapy • Average maximal mass diameter: 3.1cm(1.0-11.0cm)

11. 55/58(95%): adequate52/58(90%): diagnosticRCC: 36/52(69%)Benign: 14/52(27%)Lymphoma:1Metastasis: 1

12. Benign lesion: • Oncocytoma 12% • Angiomyolipoma 4% • Focal glomerulosclerosis 4% • Metanephric adenoma, scar, infarct, chronic glomerulonephritis

13. 47 biopsies performed before percutaneous ablation • 12/47(26%): benign • 30/47(64%): malignant • 5/47(11%): nondiagnostic • 8 patient received surgical resection • 6 patients were not treated with ablation, but biopsy showed RCC • 1 patient was metanephric adenoma • 1 patient was classified as scar, but the mass • enlarge on F/U: surgical specimen showed RCC( the only false negative in this study)

14. F/U of 14 benign biopsies • 8 have negative imaging F/U over 20.3 months(1-86 months) • 2 have negative clinical F/U over 15 and 18 months • 2 lost F/U • 1 died due to respiratory failure

15. Complication • No complication after biopsy only • 2 patients developed postprocedure perinephric hematomas after radiofrequency ablation • No transfusion or admission were required • No statistically significant difference between diagnostic yield and biopsy needle

16. Adequate smples were obtained in all cases with more than 2 passes • 19 specimens prepared with immunohistochemistry, definitive histologic diagnosis was made in 17

17. Discussion • Biopsy of the solid renal mass was not a routine before surgery • Difficulty in distinguishing low-grade malignancy from oncocytoma • Heterogeneous tumor composition with sampling error • Theory of tumor seeding of biopcy track(rare)

18. Discussion • This study shows a diagnostic yield of 90% better than older literature • Improved biopsy techniques • Advances in pathologic analysis • In this study, 27% of diagnostic biopsy was benign, one large surgical series in 2770 patients showed 13% was benign and 46% was benign with <1cm mass • Advances in immunohistologic stains improving diagnostc capabilities of pathologist - If imaging-guided biopsy is diagnostic and accurate, unnecessary surgery on benign masses may be prevented

19. Pretreatment diagnosis benefits - Malignancies other than RCC or different grade of RCC may need different treatment:

20. Correlation with imaging finding and clinical finding is critical when a negative biopsy result is obtained. • At least two passes of biopsy was suggested • The type of needle should be chosen under individual preference due to no statistically significance

21. Although biopsy of large masses or masses showing clear evidence of malignancy remain unnecessary, biopsy of small indeterminate renal masses may be appropriate