1. Cancer, kidney -- Mayo Clinic
In adults, the most common type of kidney cancer is renal cell carcinoma (renal adenocarcinoma), which begins in the cells that line the small tubes within your kidneys. Kidney cancer cells may also spread (metastasize) outside your kidneys to...
http://www.mayoclinic.com/invoke.cfm?objectid=162FE2ED-4D6F-4BB4-9DF39A9952A1A2...

2. Kidney cancer -- Information from Health A to Z
It is not practical to remove a kidney when the patient has only one kidney or when both kidneys have tumors. Renal cell carcinoma, which occurs in the cells lining the kidneys (epithelial cells), is the most common type of kidney cancer.
http://www.healthatoz.com/healthatoz/Atoz/ency/kidney_cancer.jsp

3. Kidney Cancer -- National Library of Medicine
Directory of Kidney and Urologic Diseases Organizations (National Kidney and Urologic Diseases Information Clearinghouse). Kidney Biopsy (National Institute of Diabetes and Digestive and Kidney Diseases).
http://www.nlm.nih.gov/medlineplus/kidneycancer.html