Wilms' tumor is a cancer of the kidney that primarily affects children. Also known as nephroblastoma, it's the most common malignant tumor of the kidney in children. The peak time of Wilms' tumor occurrence is at age 3, and it occurs only rarely after age 8.
The condition is named for Carl Max Wilhelm Wilms, a 19th-century German surgeon who recognized that the cancer develops from immature kidney cells. Wilms' tumor may arise in either kidney. Rarely, it affects both kidneys.
The outlook for children with Wilms' tumor has greatly improved in recent decades. Improved imaging techniques help doctors to determine the extent of the cancer in Wilms' tumor and to plan treatment.
Essential for life, your kidneys are two bean-shaped organs near the middle of your back. They cleanse your blood and maintain normal levels of body water and important chemicals, such as sodium and potassium. They also help regulate your blood pressure. Blood travels through the renal arteries to your kidneys, which filter out waste products, unneeded electrolytes and extra water and excrete them as urine. Urine leaves your kidneys through two tubes (ureters) and flows to
your bladder for storage until you urinate. Urine leaves your bladder through a narrow tube called the urethra.
In Wilms' tumor, doctors believe the cancer arises when cells destined to form the kidney fail to develop and instead multiply in their primitive state. The tumor usually becomes evident between ages 1 and 5. The mass often distorts the kidney and can compress normal tissue into a thin rim. It may cause bleeding and can result in blood in the urine.
Most cancers occur after damage to genes, sets of instructions within cells that direct the manufacture of every structure of the body. Genes program cells to develop, grow, mature and die. Cancer results when changes (mutations) arise in genes that control growth, allowing cells to multiply without restraint. In rare cases, genetic defects pass from parent to child.
Some cases of Wilms' tumor are related to defects in one of two genes on chromosome 11. They are called Wilms' tumor 1 and Wilms' tumor 2 (WT1 and WT2). WT1 appears to be critical to the development of the genitals and urinary system. Scientists believe that mutations in other chromosomes also may play a role in Wilms' tumor.
Wilms' tumor occurs more frequently in children with certain abnormalities present at birth, including:
Other abnormalities are related to the genitals and urinary system, including:
- Aniridia. In this rare condition the iris — the membrane that gives the eye its color and controls the amount of light entering the eye — fails to form completely.
- Hemihypertrophy. This abnormality occurs when one side of the body is noticeably larger than the other side.
Wilms' tumor can occur as part of rare syndromes, including:
- Cryptorchidism. One or both testicles fail to descend into the scrotum.
- Hypospadias. The urinary (urethral) opening is not in its normal position at the tip of the penis, but is on the underside.
When to seek medical advice:
- WAGR syndrome. This syndrome includes Wilms' tumor, aniridia, abnormalities of the genitals and urinary system, and mental retardation.
- Denys-Drash syndrome. This syndrome includes Wilms' tumor, kidney disease and male pseudohermaphroditism, in which a male is born with undescended testicles.
- Beckwith-Wiedemann syndrome. Included in this syndrome are omphalocele, which occurs when the abdomen fails to close around the base of the umbilical cord and abdominal organs protrude into the base of the cord; a large tongue (macroglossia); and enlarged internal organs.
Take your child to the doctor if you detect an abdominal mass or if you notice blood in his or her urine. Other signs and symptoms — fever, high blood pressure, constipation, reduced appetite, abdominal pain and weight loss — may not on their own be associated with Wilms' tumor, but they merit a trip to the doctor for evaluation.
If your child has been treated for Wilms' tumor, report any new signs or symptoms to your child's doctor. These problems may be a sign of cancer returning or of side effects of treatment.
You may feel a mass in your child's abdomen during bathing or dressing, or your child's doctor may detect it during a routine physical examination. Wilms' tumor may also go undetected early on, because the tumors can grow large without causing pain. Your child may appear healthy or may have:
- Blood in the urine
- Reduced appetite
- Weight loss
- High blood pressure
- Stomach pain
- General discomfort (malaise)
Your child's doctor will ask about signs and symptoms, other medical problems and the mother's pregnancy. He or she will ask if there's a family history of cancer or congenital defects, particularly those of the genitals and urinary system.
Your child's doctor will perform a physical examination and order laboratory tests of blood and urine. Imaging tests are essential to help locate the tumor. They include:
- Ultrasound. This noninvasive technique uses sound waves to create images of organs.
- Computerized tomography (CT). This imaging method uses X-rays to produce detailed, cross-sectional images of the body.
- Magnetic resonance imaging (MRI). This approach uses a magnetic field and radio waves to create cross-sectional images of the body.
In addition, your child's doctor may order a chest X-ray, chest CT scan, chest MRI and bone scan to determine whether the cancer has spread beyond the kidneys.
With this information, your child's doctors can assess the extent (stage) of the cancer. Staging helps guide treatment decisions. The various stages of Wilms' tumor are:
- Stage I. The cancer is found only in the kidney.
- Stage II. The cancer has spread to the tissues and structures near the kidney, such as fat or blood vessels, but it can be completely removed by surgery.
- Stage III. The cancer has spread beyond the kidney area to nearby lymph nodes or other structures within the abdomen, and it can't be completely removed by surgery.
- Stage IV. The cancer has spread to distant structures such as the lungs, liver or brain.
- Stage V. Cancer cells are in both kidneys.
Standard treatment for Wilms' tumor is surgery and chemotherapy. The stage of the tumor and appearance of the cancer cells under a microscope help determine whether your child also needs radiation therapy.
Surgical removal of kidney tissue is called nephrectomy. The various types of nephrectomy include:
- Simple nephrectomy. In this surgery, the surgeon removes the entire kidney. The remaining kidney can increase its capacity and take over the entire job of filtering the blood.
- Partial nephrectomy. This involves removal of the tumor and part of the kidney tissue surrounding it. It's usually performed when the other kidney is damaged or has already been removed.
- Radical nephrectomy. In this type of surgery, doctors remove the kidney and surrounding tissues. Neighboring lymph nodes also may be removed.
At surgery, your child's doctor examines both kidneys and the abdominal cavity for any evidence of cancer. Samples from the kidney, lymph nodes and any tissues that appear abnormal are removed and examined by microscope to identify cancer cells.
A doctor specializing in pathology examines the tumor cells under a microscope and looks for features that indicate whether the cancer is aggressive or is susceptible to chemotherapy.
Chemotherapy uses medication to kill cancer cells. It may be given by pill, intravenous (IV) line or muscle injection.
Chemotherapy is considered systemic because it enters the bloodstream and travels throughout the body to destroy cancer cells wherever they may occur. It affects rapidly dividing cells; thus, normal cells with fast turnover — such as hair follicles, cells in the gastrointestinal tract and bone marrow, the tissue at the core of bone that manufactures blood cells — are affected as well as cancer cells. As a result, these medications can have the side effects of nausea, vomiting, loss of appetite, hair loss and low white blood cell counts. Most side effects will improve after the drug is stopped, and some may lessen during therapy. Ask your child's doctor what side effects may occur during treatment.
At high doses chemotherapy can destroy bone marrow. If your child is to undergo high-dose chemotherapy, your child's doctor may suggest that marrow be removed in advance and frozen. After chemotherapy, the marrow will be returned intravenously, a procedure called autologous bone marrow reinfusion.
Radiation therapy uses X-rays or other sources of high-energy rays to kill cancer cells. It's usually started within a few days after surgery. If your child is very young, he or she may need a sedative to remain still during treatment. A doctor specializing in radiation therapy will mark the area to be treated with a special dye. Areas that should not receive radiation are shielded. Possible side effects include nausea, fatigue and skin irritation. After treatment, be prepared to apply a sun-blocking lotion to your child's skin to avoid sunburn. Diarrhea may occur after radiation to the abdomen — ask your doctor to suggest an over-the-counter or prescription medication for relief.
Treatment regimens by stage
The treatment your child undergoes depends on the stage of the cancer, the type of cancer cell (histology), and the child's age and general health.
- Stage I or II cancer. If the cancer is restricted to the kidney or nearby structures — and the cell type is not aggressive, your child will undergo removal of the affected kidney and tissues and some of the lymph nodes near the kidney, followed by chemotherapy. Some stage II cancers are also treated with radiation.
- Stage III or IV cancer. If the cancer has spread within the abdomen and can't be completely removed without jeopardizing structures such as major blood vessels — radiation will be added to surgery and chemotherapy. Your child may undergo chemotherapy before surgery to shrink the tumor.
- Stage V cancer. If the tumor cells are in both kidneys — part of the cancer from both kidneys will be removed during surgery and neighboring lymph nodes taken to see if they contain tumor cells. Chemotherapy is used to shrink the remaining tumor. Surgery is repeated to remove as much tumor as possible while leaving functioning kidney tissue. More chemotherapy and radiation therapy may follow.
Children react differently to therapies, so adjustments may be necessary. Discuss your child's treatment plan with his or her doctor and make certain that you understand the benefits and risks before giving your consent. Ask the doctor about side effects of treatments and when to report side effects.
Your child's prognosis depends on the stage and cell type of the tumor. Most children with Wilms' tumor survive.
Considering a clinical trial
Your child will receive the best care at a major medical center whose staff has expertise in treating this form of cancer. Your child's regular doctor can arrange a referral. Because advances in treating children with Wilms' tumor have come through research, you may be asked to consider letting your child participate in a clinical trial, a carefully planned study to evaluate the benefits and risks of experimental treatments. Researchers must give you all of the available information about the trial before asking you to sign consent forms. A large percentage of children with cancer are treated in a clinical trial at some point in their illness. However, enrollment in a clinical trial is up to you and your child. Talk to your child's doctor to find out more about clinical trials.
Scientists don't know how to prevent Wilms' tumor. If your child exhibits at birth one or more of the risk factors for Wilms' tumor, his or her doctor may recommend annual ultrasound exams to detect any tumor early. If you have a family history of Wilms' tumor, tell your doctor during preconception counseling.