[MR appearance of multifocal clear cell renal cell carcinoma]

To document the magnetic resonance (MR) imaging features of multifocal clear cell renal cell carcinoma (RCC).

The MR findings of 11 cases of pathologically-proved multifocal clear cell RCCs were reviewed retrospectively from January 2008 to December 2010. All patients underwent MR in a 1.5 T or a 3.0 T scanner. The MR features of the lesions were analyzed, with emphasis on the location, the signal intensity on T2-weighted imaging (T2WI), in regards to pseudocapsule, lipid component, hemorrhage, cystic degeneration, and enhancement pattern. Meanwhile, from these six aspects, the MR appearance of renal cell carcinomas occurring in the same patient were compared.

24 tumors (mean diameter, 3.1 cm) in the 11 patients (6 men, 5 women; age range, 36-69 years; mean age, 50.6 years) were detected. Multiple lesions in bilateral kidneys were found in 9 patients (9/11), while in unilateral kidney 2 patients (2/11). Hyperintensity on T2WI were observed in 16 lesions (16/24), while hypointensity 8 lesions (8/24); pseudocapsule was seen in all lesions; hemorrhage in 4 lesions (4/24), lipid component in 12 lesions (12/24) and cystic degeneration in 18 lesions (18/24), persistent enhancement in 22 lesions (22/24) and rapid wash-out pattern in 2 lesions (2/24). All lesions showed moderate or intense enhancement. The MR appearances of lesions in the same patient were identical in 5 cases (5/11), different in 6 cases (6/11).

Multifocal clear cell RCCs occur more commonly in bilateral kidneys simultaneously than in unilateral kidney. The lesions in the same patient can show different MR imaging features, which probably facilitate the preoperative determination.