Long-Term Follow-Up in Patients Undergoing Renal Mass Biopsy: Seeding is not Anecdotal

Renal biopsy is recommended if the outcome might alter therapeutic decisions for patients who present with renal masses of unclear etiology. However, little is known about long-term risks related to this procedure.

We performed a retrospective analysis of an institutional database maintained by a tertiary referral center that included patients who underwent renal biopsies between 2003 and 2005 with a follow-up of at least 15 years. Renal biopsies were taken percutaneously with a coaxial technique according to guideline recommendations and included off-line ultrasound guidance.

We identified 106 patients who underwent biopsies for a renal mass of unclear etiology. The median age was 58.7 years (43.7-66.2). A median of 4.2 (3-6) biopsies were collected from each patient. Tumor seeding leading to local growth was identified in 6 patients (5,7%) after a median follow-up of 8.2 years. Four of these lesions that were resected exhibited the same histology as the original biopsy result; these patients experienced no further recurrence. In 45 patients (42%), the biopsy results led to a therapy other than surgery (n = 28 lymphoma, n = 6 metastasis from other malignancies, n = 11 oncocytoma). The remaining 61 patients (58%) were diagnosed with renal cell carcinoma treated either surgically or with ablation. None of the patients developed metastatic spread related to tumor seeding.

Tumor seeding after renal mass biopsy is a rare, but relevant risk associated with this procedure. As indications for renal mass biopsy increase, longer-term follow-up and improved biopsy techniques should be considered to address this complication.