Solid renal mass in the cancer patient: second primary renal cell carcinoma versus renal metastasis.

Most renal metastases are asymptomatic, occur with widespread metastatic disease, and are too small to be detected with computed tomography (CT). Rarely they form large masses. These are typically angiographically hypovascular and show only minimal CT contrast enhancement. Renal carcinoma as a second primary malignancy in the cancer patient is 4.5 times more common than mass-like renal metastases and demonstrates two CT contrast enhancement patterns. The latter include either minimal enhancement or irregular regions of intense enhancement. These CT contrast enhancement patterns of both renal carcinoma and metastasis can be used to direct the further diagnostic evaluation of these masses and distinguish between a renal metastasis or a second primary renal carcinoma in the cancer patient.