Although there have been reports of elevated serum KL-6 antigen concentrations in patients with malignant tumors, including lung cancer, breast cancer, pancreatic cancer, and hepatocellular carcinoma, no reports have indicated elevated serum KL-6 concentrations in patients with renal cell carcinoma [8, 9]. This evidence concerns the gene MUC1 and hereditary clear cell renal cell carcinoma.