Figure 3b. Recurrence of clear cell type RCC after RF ablation. (a) Contrast-enhanced excretory phase CT scan shows a 2.2 x 1.6-cm enhancing mass (arrow) in the right kidney. RF ablation was performed. (b) Contrast-enhanced excretory phase CT scan obtained 4 months after ablation shows a partially exophytic hypoattenuating lesion with peripheral linear circumferential hyperattenuation in the perirenal fat (arrowheads). (c) On a contrast-enhanced corticomedullary phase CT scan obtained 8 months after ablation, the lesion has a stable appearance. (d) Contrast-enhanced corticomedullary phase CT scan obtained 20 months after ablation shows a nodular enhancing component (arrow) in the medial portion of the ablation zone. (e) Contrast-enhanced CT scan obtained 31 months after ablation shows an interval increase in the size of the mass, a finding that represents recurrent RCC. A region of interest (circled) was placed to measure CT attenuation. (Fig 3 reprinted, with permission, from reference 12.)