Back to Annual Meeting Program

Background: Renal mass biopsy (RMB) is a diagnostic option for evaluation of a suspicious renal mass. A non-diagnostic RMB (NDRMB) offers little to resolve the diagnostic dilemma. We reviewed our RMB database to determine the predictors and outcomes of a NDRMB.
Methods: Retrospective review of 1000 RMBs (1997-2010) with IRB approval. Core needle biopsy and Fine Needle Aspiration were performed concurrently.
Results: Tumor size was 0-4cm (80%), >4-7cm (16%), >7cm (4%). 82% of lesions were solid (821) and 18% were cystic (179). 216/1000 (22%) had a NDRMB. Solid lesions had a NDRMB rate of 13% (104/821) compared with 63% (112/179) in cystic lesions (p<0.0001). The NDRMB rate increased with a decrease in tumor size (<2cm: 21%, 2-4cm: 9.5%, >4-7cm: 11%, >7cm: 6.3%; p<0.0001).
Of 216 tumors with an initial NDRMB, 55 underwent repeat biopsy with a diagnostic result in 58% (32/55): 47% (26/55) RCC, 5.5% (3/55) oncocytoma, and 3.6% (2/55) angiomyolipoma. 42% (23/55) remained non-diagnostic after repeat biopsy.
33/216 (15.3%) of masses with an initial NDRMB went to surgery: 91% (30/33) were RCC or other malignancy on surgical pathology.
Conclusions: Cystic lesions have a five-fold higher chance of a NDRMB than solid lesions. Lesions <2cm have the highest risk of a non-diagnostic biopsy result. Masses with a NDRMB still have a significant risk of malignancy and therefore must be treated or followed closely.

Outcomes of Non-Diagnostic Biopsies (n=216)

Lesions undergoing repeat biopsy	55/216 (25.5%)
Diagnostic Repeat Biopsy	32/55 (58%)
RCC or other malignancy	26/55 (47%)
Oncocytoma/Oncocytic neoplasm	3/55 (5.5%)
Angiomyolipoma	2/55 (3.6%)
Non-Diagnostic Repeat Biopsy	23/55 (42%)
Surgically treated after initial NDRMB	33/216 (15.3%)
RCC or other malignancy	30/33 (91%)