Renal mass biopsy is generally safe. Minor complications occur in approximately 5% of all biopsies and major complications are rare.12 The most common complication is bleeding, which is often subclinical and self-limited. Microscopic hematuria is frequently seen but gross hematuria is rare and suggests inadvertent biopsy of normal renal parenchyma. Arteriovenous fistula, though rare, should be considered in cases of persistent bleeding. Pseudoaneurysm formation is also rare and may not manifest for several months after biopsy.

Concern for bleeding is greatest with angiomyolipomas because of their hypervascularity and potential to bleed spontaneously. Pneumothorax may occur in 14%-29% of cases, although it is often clinically insignificant.13,30 The risk is greatest when biopsy is performed from the posterior approach and may be lessened by performing the puncture during expiration with needle positioned subcostally. Tumor seeding is an often reported objection to percutaneous biopsy, but the overall estimated risk is less than 0.01%. There have only been six reported cases from 1977 to 1999 and no cases reported in over a decade.13

There is a greater risk of seeding with transitional cell carcinomas than with RCC, so it is recommended that percutaneous biopsy be avoided when there is any concern that the tumor might be transitional cell carcinoma and not a renal cortical neoplasm.30 In patients who are planned to undergo ablation, tumor biopsies may be taken immediately after ablation to minimize risk of seeding as well as bleeding. RCC can be identified by the pathologist based on its architecture after either RFA or cryoablation and post-ablation biopsy does not decrease diagnostic yield.31

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Biopsy costs

From a financial perspective, a recent study found biopsy of small renal cortical neoplasms to be a cost-effective addition to the treatment algorithm.32 Pandharipande and colleagues used a decision-analytic Markov model to estimate life expectancy and lifetime costs for patients with small renal tumors less than or equal to 4 cm looking at initial biopsy to direct therapy to surgery or imaging surveillance versus empiric surgery.

Using renal mass biopsy to direct therapy resulted in a clinically insignificant difference in quality-adjusted life expectancy (four days), but a lifetime cost saving of $3,466. Their model incorporated biopsy performance, the probability of track seeding with malignant cells, the prevalence and growth of benign and malignant tumors, treatment effectiveness and costs, and patient outcomes.


While the traditional algorithm of renal mass management has not included biopsy, current advances in imaging have resulted in increased detection of small renal masses and led to increased treatment and possibly over-treatment. This carries not only financial burden for society but also significant risk for patients. Biopsy of renal masses, which is commonly performed using CT or US guidance, can be used to determine if a mass is malignant or benign and thereby avoid over-treatment.

Biopsy can be performed easily in the office by the urologist. Renal mass biopsy can be both specific and sensitive, although sensitivity is lower for small renal masses. Accuracy in determination of nuclear grade and subtype of biopsy specimens from malignant masses can be improved with PCR and FISH. With increasing use of ablative technologies for small renal masses, biopsy may take on a larger role in diagnosis prior to ablation and assessment of treatment success after ablation.

The risk of complications is low and most are minor. Major complication such as clinically significant pneumothorax and tumor seeding are rare. With improvements in imaging and development of new immunohistochemical markers, renal mass biopsy is sure to be used more frequently in the diagnostic and treatment algorithms of renal masses.

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