Nonrenal cancers may metastasize to the kidneys. The most common cancers that metastasize to the kidney are melanomas and solid tumors, particularly lung, breast, stomach, gynecologic, intestinal, and pancreatic. Leukemia and lymphoma may invade the kidneys, which then appear enlarged, often asymmetrically.
Despite extensive interstitial involvement, symptoms are rare, and renal function may not change from baseline. Proteinuria is absent or insignificant, and blood urea and creatinine levels rarely increase unless a complication (eg, uric acid nephropathy, hypercalcemia, bacterial infection) occurs.
Renal metastases are usually discovered during evaluation of the primary tumor or incidentally during abdominal imaging. If there is no known primary tumor, diagnosis proceeds as for renal cell carcinoma.
Treatment is systemic therapy for the primary tumor and, rarely, surgery. However, partial nephrectomy may be necessary to guide choice of systemic therapy in cases where core needle biopsy is unable to provide sufficient tissue.