Fig. 5.

In this figure the difference in appearance and enhancing pattern of clear cell and papillary renal cell carcinoma are shown. The first case (A-C) concerns a 41-year-old women referred for analysis of an incidentaloma of the right kidney detected on ultrasound. A 3-phase CT scan showed a 36-mm large tumor of the lower pole of the right kidney with a typical gradual enhancement pattern with, as opposed to the clear cell RCC case, no washout in the nephrogenic phase. On unenhanced CT, the tumor appears homogeneous and the Hounsfield unit value of the tumor was 31. (A) The corticomedullary (B) and nephrogenic phase (C) showed homogeneous enhancement of the tumor with Hounsfield unit values of 31 and 68, respectively. Histopathology after robot-assisted partial nephrectomy confirmed the diagnosis of a 38-mm large, Furhman grade 4 papillary renal cell carcinoma. The second case (D-F) concerns a 67-year-old man in whom an incidentaloma in the right kidney was found on MRI of the spinal canal. The tumor was evaluated through a CT scan which showed a 67 mm large, interpolar tumor of the right kidney. The non-contrast phase showed a heterogeneous aspect with mixed attenuation (A), in the corticomedullary phase strong enhancement of the solid parts is seen (B) with subsequent washout in the nephrogenic phase (C). The latter is best seen when comparing the enhancement with the renal cortex.