Figure 17c. Discordant imaging findings in an 82-year-old man with a 13-cm-diameter cystic mass in the upper renal pole. (a) Unenhanced CT scan obtained through the mass shows two irregular nodular regions of calcification (arrows). (b) Contrast-enhanced CT scan obtained at the same level shows no enhancement near the calcifications, the wall, or the center of the mass. There were no suspicious areas on other scans. On the basis of the CT findings, the mass could have been managed with follow-up. (c) Longitudinal sonogram obtained through the mass shows that the lesion (arrows) is complex and solid appearing with several central, irregular hypoechoic areas. The mass was excised and diagnosed as a "burned-out" renal cell carcinoma without viable tumor cells. K = kidney.