PURPOSE: Radio frequency ablation is an emerging nephron sparing treatment 
option in select patients with small renal tumors. Some have questioned the 
completeness of cell death and the reliability of axial imaging for radio 
frequency ablation followup. We present results in patients with no evidence of 
radiographic active disease who underwent biopsy more than 1 year following 
ablation.
MATERIALS AND METHODS: Patients who had no clinical evidence of disease, defined 
as absent lesion growth and contrast enhancement on computerized tomography, 1 
year or more following radio frequency ablation underwent percutaneous renal 
biopsy to evaluate cell viability in the ablative zone. A total of 19 patients 
(20 lesions) were included in the study. Histological comparison of pre-ablation 
and post-ablation specimens was performed using hematoxylin and eosin staining.
RESULTS: Pre-ablation biopsies confirmed that 17 of 20 tumors were renal cell 
carcinoma, while the remaining 3 were oncocytoma. Following ablation at a mean 
followup of 26.9 months (range 13.1 to 58.0) all 20 lesions were stable in size 
without evidence of contrast enhancement on computerized tomography. At repeat 
biopsy all histology specimens showed unequivocal tumor eradication with no 
evidence of cellular viability. Histological changes beyond 1 year demonstrated 
coagulative necrosis, hyalinization, inflammatory cell infiltration and residual 
ghost cells.
CONCLUSIONS: Pathological examination of radiographically negative lesions 
biopsied more than 1 year following radio frequency ablation confirmed no 
evidence of disease in all specimens. Therefore, axial imaging can reliably 
monitor treatment efficacy in the long term. Chronic changes after radio 
frequency ablation demonstrate coagulative necrosis and nonviable cells. This 
suggests an evolution of pathological changes that renders early post-ablative 
biopsy unreliable.