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BACKGROUND: Tuberous sclerosis is genetic condition associated with a reported 50-60% risk of renal angiomyolipomas (AMLs) and a 2-4% risk of RCC. Unfortunately, current CT and MR technology is unable to reliably discriminate between an AML with little lipid content and a renal carcinoma. We present the first published series of CT-directed percutaneous biopsies of these lesions in patients with tuberous sclerosis and report outcomes with respect to accuracy of diagnosis and complications from the procedure.
METHODS: We performed a retrospective IRB-approved review of our electronic records from July 2000 to November 2011 from our tuberous sclerosis clinic. We selected all patients who underwent biopsy for a lipid-poor, suspicious solid renal tumor. We recorded biopsy pathology, all complications, and correlated biopsy with final pathology when extirpative procedures were undertaken.
RESULTS: 23 of patients (14F:9M) underwent a total of 25 biopsies during the study period. Age ranged from 7.6-61.2 years (median 34.1). There were no Clavien-grade complications; no patients required blood transfusion, and no renal units were lost as a complication of the biopsy. Two patients (ages 7.6 and 11.2) were admitted after the procedure as planned; all others were performed as outpatient procedures. The procedures were performed using a coaxial 17 gauge Temno needle with core biopsy and FNA under CT guidance.
Three lesions were biopsied under general anesthesia and the remaining 22 lesions were biopsied under sedation or local anesthetic alone. The lesions ranged from 1.2 - 19cm (median 1.3 cm), 17L:8R. Mean length of clinical follow-up was 4.03 years, and mean length of imaging follow-up was 3.4 years. One patient underwent radical nephrectomy for what was biopsied as an epitheliod neoplasm and determined to be a 15 cm AML on final pathology; this was in the first year of our series, and there were no known diagnostic discrepancies since. 17 lesions were diagnosed as AML, 4 as oncycytic neoplasms (oncocytoma or otherwise), and 4 as clear cell renal cell carcinoma.
CONCLUSIONS: Percutaneous biopsy for lipid-poor solid renal tumors in patients with tuberous sclerosis is a well- tolerated and effective solution for distinguishing benign from malignant renal lesions, a common clinical dilemma in this population. The high rate of diagnosis clear cell carcinoma (16%) suggests that these lesions demand attention, and a single cross sectional imaging modality does not provide sufficient information. Percutaneous biopsy can be viewed as a safe addition to a nephron- sparing program for managing these lesions in this population.