Figure 10b. Renal aspergillosis in an 18-year-old man with acute myeloid leukemia who presented with fever and left flank pain. (a) Axial unenhanced CT scan shows a lobulated masslike lesion (arrows) with focal internal high attenuation, a finding suggestive of intralesion hemorrhage. (b) Coronal reformatted contrast-enhanced CT scan obtained during the excretory phase shows the poorly enhancing, low-attenuation, masslike renal parenchymal lesion extending to the renal sinus (arrow). Analysis of the nephrectomy specimen demonstrated a hemorrhagic mass due to focal invasive aspergillosis. Aspergillosis causes vascular occlusion and multiple renal infarcts. However, as in this case, differentiation from a tumor is not always easy.