Cancer, kidney: Malignancy of the kidney, the organ that is primarily responsible for the removal of metabolic products from the body. The types of kidney cancer in adults and children are different and distinct:

• Adults -- Kidney cancer tends to occur after age 50 and strikes men twice as often as women. The most common type occurs in the renal (kidney) tissue that filters the blood and produces the urine and is called renal cell cancer (or renal cell carcinoma). Another type of adult kidney tumor arises in the renal pelvis where the urine collects and is called transitional cell carcinoma. The most frequent diagnostic sign of kidney cancer in adults is blood in the urine.
• Children -- Far and away the main type of kidney cancer in children is Wilms tumor. It starts to develop in fetal life and may be large by the time it is detected (on the average at 3 years of age). Wilms tumor is associated with certain congenital defects including urinary tract abnormalities, absence of the iris (aniridia) and hemihypertrophy (enlargement of one side of the body), and shows an increased incidence among siblings and twins. The tumor tends to cause a noticeable mass and sometimes pain in the abdomen. Blood in the urine occurs in a minority of cases.

Kidney cancer is treated with surgery, embolization, radiation therapy, hormone therapy, biological therapy, or chemotherapy.