Kidney cancer occurs when cells in the kidney divide without control or order, forming a growth called a tumor and sometimes spreading to other parts of the body.
The kidneys are two bean-shaped organs located near the spine. Their main function is to filter salts, excess water, and impurities from the blood, producing the liquid waste called urine. Urine drains from the kidneys through a tube called the ureter (YOOR-eh-ter) to the bladder where it is stored until it leaves the body through another tube called the urethra (yoo-REE-thra). Besides the job of filtration, the kidneys also help to produce red blood cells and to maintain healthy blood pressure.
If cancer develops in the kidneys, it may affect not only the kidneys but nearby organs as well, including the liver, pancreas, and large intestine. In addition, kidney cancer cells may spread through the bloodstream or lymphatic system to other parts of the body. The most common form of kidney cancer in children is Wilms' tumor, and the most common form of kidney cancer in adults is renal cell cancer.
Wilms’ tumor, the most common cause of kidney cancer in children, begins to develop even before a child is born. As the fetus grows in the womb, the kidney cells develop into netlike structures of blood vessels and tissues that are designed to filter the blood. When these cells do not mature as they should, the baby is born with some underdeveloped cells. Usually, these cells mature by the time a child is three or four years old. Sometimes, however, they start to grow out of control, forming a jumbled mixture of small cells called a Wilms' tumor. The tumor is named after the German doctor Max Wilms (1867–1918), who first wrote about it in 1899.
Doctors find the tumor by feeling for a mass while examining a baby's belly. The baby usually has few, if any, symptoms. If the tumor has not spread beyond the kidney, the outlook for the child's recovery is excellent. Most children with Wilms’ tumor undergo surgery or chemotherapy * . If the cancer has spread beyond the kidney, doctors may also prescribe radiation therapy, which uses focused, high-energy rays to destroy cancer cells.
Kidney cancer in adults, which is much more common than in children, occurs only rarely in people younger than 45 years of age. Overall, medical professionals diagnose more than 50,000 cases of the disease in the United States each year. In four out of five cases, the tumor forms in the tissue responsible for filtering the blood, but it also can affect the renal pelvis, the structure that collects the urine after filtration. Unlike Wilms' tumor, kidney cancer in adults often spreads to nearby organs and to other parts of the body.
Kidney cancer is more common in people who smoke cigarettes. Exposure to certain chemicals and to medications containing the pain reliever phenacetin (fe-NES-a-tin) appears to increase risk for the disease. Heredity can play a role, too. Many cases of kidney cancer, however, develop without apparent cause. The most common early symptoms of kidney cancer include the following:
Doctors start with a medical history, a physical examination, and laboratory tests of blood and urine samples. Based on their findings, they may order tests that produce pictures of the kidneys and nearby organs. They may also order additional tests, including the following:
If a doctor suspects kidney cancer, a surgeon will perform a biopsy by inserting a thin needle into the tumor and removing a sample of tissue to be examined under the microscope. If these cells turn out to be cancerous, doctors need to find out whether the cancer has spread beyond the kidney. Kidney cancer cells often spread through the bloodstream or the lymph nodes * , which filter the infection-fighting fluid called lymph. Doctors may order more imaging tests to examine nearby organs and to check for swollen lymph nodes in the chest and abdomen. They may also order chest x-rays and bone scans because the cancer tends to spread to the lungs or the bones.
The way the disease is treated depends on whether it has spread beyond the kidney. If it has not spread elsewhere, the most common treatments are surgery and radiation therapy. Surgery involves removing part or all of the kidney, a procedure called nephrectomy (nef-REK-tom-ee). The remaining kidney generally is able to perform the work of both kidneys. Kidney cancer that has spread to other parts of the body can be very difficult to treat. Two treatment options are biological therapy and chemotherapy. Biological therapy, also called immunotherapy, attempts to boost the body's own natural defenses against the cancer. Medical professionals prescribe immune boosters, such as Interleukin-2 and interferon. Chemotherapy delivers anticancer drugs into the person's bloodstream through a needle or in pill form.
In addition to these treatment options, people with advanced kidney cancer and their caregivers may find support groups to be a valuable resource.
See also Cancer: Overview • Hypertension • Tumor
Campbell, Steven C., et al. 100 Questions & Answers about Kidney Cancer, 2nd ed. Burlington, MA: Jones & Bartlett, 2015.
American Cancer Society. “Kidney Cancer.” http://www.cancer.org/cancer/kidneycancer/index (accessed October 20, 2015).
Centers for Disease Control and Prevention. “Kidney Cancer and the Environment.” http://ephtracking.cdc.gov/showCancerKidneyRenalEnv.action (accessed October 20, 2015)
National Cancer Institute. “Kidney Cancer—For Patients.” http://www.cancer.gov/types/kidney (accessed October 20, 2015).
American Cancer Society. 250 Williams St. NW, Atlanta, GA 30303. Toll-free: 800-227-2345. Website: http://www.cancer.org (accessed October 20, 2015).
Kidney Cancer Association. PO Box 803338 #38269, Chicago, IL, 60680-3338. Toll-free: 800-850-9132. Website: http://www.kidneycancer.org (accessed October 20, 2015).
National Cancer Institute. BG 9609 MSC 9760, 9609 Medical Center Dr., Bethesda, MD, 20892-9760. Toll-free: 800-4-CANCER. Website: http://www.cancer.gov (accessed October 20, 2015).
* chemotherapy (KEE-mo-THER-apee) is the treatment of cancer with powerful drugs that kill cancer cells.
* CT scans, computed tomography (to-MOG-ra-fee) scans, or CAT (computerized axial tomography) scans, use computers to view structures inside the body.
* MRI, short for magnetic resonance imaging, produces computerized images of internal body tissues based on the magnetic properties of atoms within the body.
* ultrasound, also called a sonogram, is a diagnostic test in which sound waves passing through the body create images on a computer screen.
* lymph nodes (LIMF nohds) are small, bean-shaped masses of tissue containing immune system cells that fight harmful microorganisms. Lymph nodes may swell during infections.