Blood and urine samples are collected. Samples are evaluated by immunoblotting to detect bone morphogenetic protein antagonist regulated in cancer (BARC) and by mass spectrometry analysis to detect hepcidin levels. Serum samples are further analyzed for serum iron, ferritin, and total-iron body capacity. Histology of biopsy samples will be recorded for patients undergoing nephrectomy for renal cell carcinoma. These patients will undergo a second collection of blood and urine samples 3 months post-nephrectomy.