Multilocular cystic renal cell carcinoma presenting as a solid mass: radiologic evaluation.

BACKGROUND

Multilocular cystic renal cell carcinomas (MCRCCs) are a recently described variety of renal cell carcinoma with characteristic pathological and clinical features. We found that the radiologic appearances of MCRCCs of smaller size did not fulfill the previously documented criteria of the MCRCCs. This study was conducted to analyze the radiologic characteristics of MCRCCs of smaller sizes.

METHODS

The radiologic findings of 13 multilocular cystic renal cell carcinomas of diameter ranging from 10-32 mm (average 22 mm) seen in nine patients were analyzed in correlation with pathologic findings.

RESULTS

On US, the tumors were predominantly hyperechoic (11 of 13 tumors) with or without small anechoic areas. Precontrast CT showed the lesions to be either hypodense or hyperdense depending on the presence of hemorrhage. Degree of contrast enhancement was usually slight. The mean increase in CT attenuation was 28 +/- 19 (mean +/- standard deviation) at dynamic phase and 12 +/- 10 at delayed phase. On MR imaging, signal intensities of the tumors were high both on T1- and T2-weighted images (7 of 9 tumors) due to proteinaceous fluid or hemorrhage. Dynamic enhanced MR imaging revealed irregular contrast enhancement within the tumor (5 of 6 tumors). Angiography failed to reveal neovascularity.

CONCLUSION

Although multiple cysts were seen within the tumors pathologically, MCRCCs of smaller sizes appeared solid on radiologic examinations. However, contrast enhancement or neovascularity was very slight.