Computed tomography of internally calcified renal cysts.

Three benign renal cysts containing nonperipheral calcifications on CT are presented. Renal cyst puncture and cytologic examination of the aspirate confirmed their benign nature. Calcification, either peripheral or within the mass, may occur in benign or malignant cystic lesions of the kidney. The demonstration of calcification is a definite indication for cyst puncture to avoid unnecessary surgery or overlooking a possible malignancy.