The kidneys filter blood to remove impurities, excess minerals and salts, and extra water. They also produce hormones that help control blood pressure, red blood cell production, and other bodily functions.
Forms of kidney cancer
Renal cell carcinoma (RCC) is the most common type of adult kidney cancer, accounting for about 85 percent of all kidney cancer diagnoses. Subtypes of RCC can be a factor in treatment options. The most common subtype is clear cell renal cell carcinoma (about 70 percent of RCC cases), followed by papillary renal cell carcinoma (about 10 percent of RCC cases) and chromophobe renal cell carcinoma (about 5 percent of RCC cases). Other subtypes of RCC are very rare and include collecting duct RCC, multilocular cystic RCC, medullary carcinoma, mucinous tubular and spindle cell carcinoma, neuroblastoma-associated RCC, and unclassified RCC.
Urothelial carcinoma, also called transitional cell carcinoma, accounts for 10 to 15 percent of all kidney cancers diagnosed in adults. This cancer doesn’t start in the kidney itself, but in transitional cells where the ureters meet the kidneys.
Renal sarcomas make up less than 1 percent of all kidney cancers. They begin in the blood vessels or connective tissue of the kidney.
Wilms tumor (nephroblastoma) is most common in children and is treated differently from kidney cancer in adults. When combined with surgery, this type of tumor is more likely to be successfully treated with radiation therapy and chemotherapy than the other types of kidney cancer.
Lymphoma can enlarge both kidneys and is associated with enlarged lymph nodes in other parts of the body, including the neck, chest, and abdominal cavity. In rare cases, kidney lymphoma can appear as a lone tumor mass in the kidney and may include enlarged regional lymph nodes.
Risk factors for kidney cancer
Smoking — Smoking tobacco doubles the risk of developing kidney cancer. It is believed to cause about 30% of kidney cancers in men and about 25% in women. The risk drops if you stop smoking, but it takes many years to get to the risk level of someone who never smoked.
Gender — Men are two to three times more likely to develop kidney cancer than women.
Race — African Americans and Native Americans/Alaska Natives have slightly higher rates of RCC than do whites.
Age — Kidney cancer is typically found in adults and is usually diagnosed between the ages of 50 and 70.
Obesity — People who are very overweight have a higher risk of developing RCC, possibly due to hormone changes from obesity.
High blood pressure — Kidney cancer risk increases in people with high blood pressure. Some studies have suggested that certain medicines used to treat high blood pressure may raise the risk of kidney cancer, but it is hard to tell whether this increased risk is due to the condition, the medicine used to treat it, or both.
Overuse of certain medications — Painkillers containing phenacetin have been banned in the United States since 1983 because of their link to transitional cell carcinoma. Diuretics and analgesic pain pills, such as aspirin, acetaminophen, and ibuprofen, have also been linked to kidney cancer.
Exposure to cadmium and other chemicals — Some studies have shown a connection between exposure to the metallic element cadmium and kidney cancer. Working with batteries, paints, or welding materials may increase a person’s risk as well. This risk is even higher for smokers who have been exposed to cadmium. Workplace exposure to other chemicals (such as some herbicides) and organic solvents (particularly trichloroethylene) has been linked to an increased risk of RCC.
Chronic kidney disease — People who have decreased kidney function but don’t yet need dialysis may be at higher risk for the development of kidney cancer.
Long-term dialysis — People who have been on dialysis for a long time may develop cancerous cysts in their kidneys. These growths are usually found early and can often be removed before the cancer spreads.
Family history of kidney cancer — People who have first-degree relatives (parents, siblings, or children) with kidney cancer have an increased risk of developing the disease. This risk increases if a number of extended family members have been diagnosed with kidney cancer, including grandparents, aunts, uncles, nieces, nephews, grandchildren, and cousins, and if these family members were diagnosed before the age of 50, had cancer in both kidneys, and/or had more than one tumor in the same kidney.
Genetic conditions — Although kidney cancer can run in families, inherited kidney cancers occur only about 5 percent of the time. People who have the following conditions have a higher risk of getting kidney cancer: Von Hippel-Lindau syndrome (VHL), hereditary non-VHL clear cell renal cell carcinoma, hereditary papillary renal cell carcinoma (HPRCC), Birt-Hogg-Dubé syndrome (BHD), hereditary leiomyomatosis and renal cell carcinoma (HLRCC), tuberous sclerosis complex (TSC), familial renal cancer, Cowden syndrome, and hereditary renal oncocytoma.
Symptoms of kidney cancer
Blood in the urine
Pain or pressure in the side or back
A mass or lump in the side or back
Swelling of the ankles and legs
High blood pressure
Anemia (low red blood cell counts)
Loss of appetite
Unexplained weight loss
Fever that keeps coming back and is not from a cold, flu, or other infection.
For men, a rapid development of a cluster of enlarged veins known as a varicocele, around a testicle, particularly the right testicle, may indicate that a large kidney tumor may be present.
How is kidney cancer treated with radiation?
External-beam radiation therapy (EBRT) is the type of radiation therapy used most often for kidney cancer. Radiation is very rarely used alone to treat kidney cancer because of the damage it causes to the healthy kidney.
Radiation may be used only if a patient cannot have surgery and, even then, usually only on areas where the cancer has spread and not on the primary kidney tumor.
Radiation may be used as palliative therapy to help ease symptoms, such as pain, bleeding, or problems caused by the spread of cancer (especially to the bones or brain).
More extensive information about kidney and other cancers may be found at these sites:
American Cancer Society: Cancer.org
American Society of Clinical Oncology: Cancer.net
National Cancer Institute: Cancer.gov