[918] Pathologic Findings in Needle Core Biopsies of Renal Tumors Treated with Ablation Therapy

Rafael E Jimenez, Christine M Lohse, Thomas D Atwell, Grant D Schmit, Anil N Kurup, John C Cheville. Mayo Clinic, Rochester, MN

Background: Renal tumor ablation (RTA) by radiofrequency or cryotherapy is a viable option in the management of renal tumors and/or tumor recurrences. It is frequently preceded by a needle core biopsy (NCB) for histologic documentation of the tumor. We investigated whether pathologic features in the NCB predict technical failure (TF) or recurrence after RTA.
Design: NCB material from 385 tumors from 356 procedures among 341 patients were reviewed and findings were correlated with incidence of local recurrence and TF. TF was defined as radiological evidence that the ablation effect had not extended beyond the edges of the tumor.
Results: The mean age of patients was 69.6 years (range 24 - 91). The mean tumor size was 2.8 cm (range 0.6 - 8.8). NCB was positive (pos) for tumor in 299 cases, while in 86 it was negative (neg) or equivocal. 14 neg cases had concomitant smears of aspirated material that were considered pos (11), suspicious (2), or atypical (1). Histologic types on core-pos cases included 151 clear cell renal cell carcinoma (RCC), 51 papillary RCC, 44 oncocytoma, 7 chromophobe RCC, 11 oncocytic neoplasm NOS, 6 metastatic tumors to the kidney, 7 angiomyolipoma, 3 clear cell papillary RCC, 6 unclassifiable malignant tumors, 2 sarcomatoid RCC, and 4 other benign lesions. Fuhrman nucleolar grade for RCC cases was 1 in 17%, 2 in 67%, 3 in 12%, and 4 in 3%. Vascular invasion, sarcomatoid change, and tumor necrosis were seen in 4%, 3%, and 0% of RCC cases, respectively. Two (0.5%) technical failures were observed, both in clear cell RCC. 329 tumors were followed for at least 3 months. Of these, 8 (2.4%) recurred at a mean of 2.3 years following RTA (range 0.8 - 4.5) of which 6 were clear cell RCC while 2 had a neg biopsy. Mean follow-up for the 321 tumors that did not recur was 2.3 years (range 0.3 -10.3). Estimated recurrence-free survival rates (95% CI; number still at risk) at 1, 3, 5, and 7 years following RTA were 99.6% (98.9 -100; 234), 96.2% (93.2 - 99.4; 97), 93.2% (88.1 - 98.7; 32), and 93.2% (88.1 - 98.7; 10), respectively.
Conclusions: Recurrence and TF are uncommon events in cases of RTA. NCB of pre-ablated tumor may render important information in planning follow-up of patients after RTA. However, no pathologic finding was able to predict outcome, given the low frequency of events in these series. Oncocytic neoplasms did not recur independently of type or certainty of histology.
Category: Genitourinary (including renal tumors)

Tuesday, March 5, 2013 8:15 AM

Proffered Papers: Section A, Tuesday Morning


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