Seminar article
Evolving role of renal biopsy in small renal masses

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Abstract

Historically, patients with small renal masses have not routinely undergone percutaneous biopsy before proceeding to surgical extirpation, partly due to concerns of biopsy inaccuracy, needle track seeding, and minimal change in clinical management. However, contemporary improvements in technique and cross-sectional imaging have led to increased diagnostic sufficiency and accuracy of renal biopsy. Major complications are rare. Most importantly, a large proportion of small renal masses biopsied are, in fact, benign, and biopsy has the potential to change clinical management and help patients avoid unnecessary surgical extirpation. Image-guided percutaneous core biopsy should be incorporated into the diagnosis and management of enhancing small renal masses.

Introduction

The increasing incidental diagnosis of small renal masses (SRMs) ≤4 cm with cross-sectional imaging accounts partially for the rising incidence of kidney cancer [1], and especially in surgically unfit patients, can pose a clinical dilemma. While biopsy is already used routinely with little morbidity when attempting to document metastatic or systemic disease involvement of the kidney, biopsy has not been used routinely in the diagnosis and management of small renal neoplasms, unlike in other urologic cancers, in which biopsy is performed in nearly all cases and subsequent pathology guides treatment decisions. Classically, patients with clearly enhancing renal lesions have been directed towards surgical intervention, even though some complex lesions cannot be characterized as malignant on imaging [2]. Furthermore, a third of SRMs are benign [3] and only a minority will grow significantly if managed conservatively [4], indicating possible overtreatment of these lesions with surgery. Ultimately, image-guided percutaneous core biopsy should be utilized to a greater degree for enhancing small renal masses, as results may significantly help tailor management.

Section snippets

Diagnostic accuracy

Historical arguments against utilization of biopsy have included a lack of sufficient tissue obtained, lack of accuracy, inability to type and grade the biopsy material, seeding of the needle track, and minimal change in clinical management. Initial concerns regarding biopsy inaccuracy stemmed from early studies of fine-needle aspiration, in which the diagnostic yield was not sufficient to warrant the potential morbidity [5]. Additionally, previous reasons for biopsy failure include sampling of

Complications

Major complications from biopsy are infrequent and include bleeding with development of a perinephric hematoma, delayed arteriovenous fistula, pneumothorax, and tumor track seeding. In particular, tumor track seeding is a worrisome complication but rare (<0.01%) and not seen at all in more contemporary studies, likely due to coaxial biopsy technique. Overall morbidity from biopsy is quite low, and mortality is exceedingly rare.

University of Michigan experience

In an upcoming study, we will report the use of renal biopsy, particularly in SRMs ≤4 cm [12]. We demonstrated a high rate of diagnostic sufficiency (91%) in 110 biopsies performed at our institution from 1999 to 2006. At least 2 cores were obtained with an 18 gauge biopsy needle. Most significantly, accuracy of biopsy compared with nephrectomy was 100% in 35 patients who underwent surgical extirpation, and accuracy of RCC subtype was 96.6% (with 1 case of clear cell RCC noted on biopsy,

Limitations

Limitations of renal biopsy should be recognized. False-negative results are uncommon but can arise from tumor heterogeneity or suboptimal collection. In a recent meta-analysis, false-negative results were reported in 4% of renal mass biopsies and false-positive results in 1.3% [14]. Concern for inadequate biopsy should prompt rebiopsy. Biopsy is also unreliable and potentially risky in cystic masses, given the lack of tissue obtained and possible tumor spillage with cyst rupture. Finally, it

Conclusions

In contemporary series, percutaneous renal mass biopsy has demonstrated high diagnostic sufficiency and accuracy, due to improvements in cross-sectional imaging and technique. Overall morbidity is low. Biopsy is already of use in documenting systemic, non-RCC disease involvement of the kidney, and may also be of great utility in patients with marginal renal function for whom the administration of intravenous contrast or gadolinium poses a risk. Furthermore, for small renal masses, a third of

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