Cystic renal cancers: CT characteristics.

The preoperative distinction between renal cyst and tumor has long been a dilemma. A cystic renal adenocarcinoma may appear similar to a largely necrotic tumor or a cancer incorporated into a cyst or arising from a cyst wall. Overall, these cystic cancers present the same preoperative features. In our series of 15 cases, the characteristic pattern on computed tomography scans included size greater than or equal to 10 cm, localized thickening of cyst walls with contrast enhancement, and irregularly and poorly defined implantation in the kidney.