This cancer forms in tissues of the kidneys. Kidney cancer includes renal cell carcinoma (cancer that forms in the lining of very small tubes in the kidney that filter the blood and remove waste products) and renal pelvis carcinoma (cancer that forms in the center of the kidney where urine collects). It also includes Wilms tumor, which is a type of kidney cancer that usually develops in children under the age of 5.
SEER Cancer Stat Facts: Kidney and Renal Pelvis Cancer. National Cancer Institute. Bethesda, MD, http://seer.cancer.gov/statfacts/html/kidrp.html