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Wilms Tumor

What is Wilms' tumor?

Wilms' tumor is a disease in which cancer (malignant) cells are found in the kidney. The kidneys are a "matched" pair of organs, so that for children with kidney cancer, the removal of a kidney is possible and a routine part of therapy for most. Inside each kidney are tiny tubes that filter and clean the blood, filtering out unneeded products, and making urine. The urine made by the kidneys passes through a tube called a ureter into the bladder where it is held until it is passed from the body. The kidneys are directly connected to veins that go to the Inferior Vena Cava, a vein running back to the heart.

Wilms' tumor occurs most commonly in children under the age of 5. Wilms' tumor is curable in the majority of affected children in that greater than 90% of patients are alive without disease four years after diagnosis. Wilms' tumor is usually found when unexpected, as it is usually a painless mass in the abdomen.

Your child's doctor will usually feel your child's abdomen for lumps. If they feel a mass, they may obtain an ultrasound which uses sound waves to make a picture, or a special x-ray called a computed tomographic scan (CT scan) to look for lumps. A special scan called magnetic resonance imaging (MRI), which uses magnetic waves to make a picture, may also be done. Chest X-rays and CT scans will be done, and a bone scan may rarely be necessary.

If tissue that is not normal is found, your child's doctor will refer you to a pediatric oncologist. If they feel this may be cancer, they will refer you to an oncologic surgeon who will cut work with your oncologist to decide what extent of surgery is best for your child up front. If complete removal of the tumor and affected kidney can be accomplished by the surgeon, it should be done.

If the tumor is too large for this, or if both kidneys have tumors, the surgeon will cut out a small piece. This is called a biopsy. Pathologists will look at it under the microscope to see if there are any cancer cells, and if so, what type of cancer it is.

Your child's chance of recovery (prognosis) and choice of treatment depend on the stage of your child's cancer (whether it is just in the kidney or has spread to other places in the body), how the cancer cells look under a microscope (whether the histology is "favorable" or "unfavorable," which is also referred to as "anaplastic"), and the tumor size/volume.

Stages of Wilms' tumor

Once Wilms' tumor has been diagnosed, more tests will be done to find out if cancer cells have spread from the kidney to other parts of the body. This is called staging. Your child's oncologist needs to know the stage and the histology of the tumor to plan treatment. Staging is based upon the amount of visible and microscopic tumor spread and is the same regardless of the histology of the tumor. The following stages are used for Wilms' tumor:

Stage I

(approximately 40% of patients)
Cancer is found only in the kidney and can be completely removed by surgery.

Stage II

(approximately 23% of patients)
Cancer has spread beyond the kidney, to fat or soft tissue, to blood vessels, or to the renal sinus (a large part of the kidney through which blood and fluid enter and exit the kidney). However, the cancer can be completely removed by surgery.

Stage III

(approximately 23% of patients)
Cancer has spread beyond the kidney within the abdomen and cannot be completely removed by surgery. The cancer may have spread to important blood vessels or the peritoneum. The cancer may also have spread to the lymph nodes (small bean-shaped structures found throughout the body that produce and store infection-fighting cells) near the kidney.

Stage IV

(10% of patients)
Cancer has spread to other parts of the body, most commonly the lungs, but rarely the liver, bone, and/or brain.

Stage V

(approximately 5% of patients)
Cancer cells are found in both kidneys at diagnosis. An attempt should be made to stage each kidney individually, according to the above criteria on the basis of extent of disease prior to biopsy.


Recurrent disease means that the cancer has come back (recurred) after it has been treated. It may come back where it started or in another part of the body.

How Wilms' tumor is treated

There are treatments for patients with Wilms' tumor. The National Wilms' Tumor study group established standard treatment for patients with Wilms tumor and this consists of:

  • surgery (taking out the cancer in an operation)
  • chemotherapy (using drugs to kill cancer cells)
  • radiation therapy (using high-dose x-rays or other high-energy x-rays to kill cancer cells), in select patients

Surgery is an important part of the treatment for Wilms' tumor. An oncologic surgeon may take out the cancer using one of the following:

  • Partial nephrectomy removes the cancer and part of the kidney around the cancer. This operation is not recommended although it may be used in special cases, such as when very small tumors are discovered by ultrasound or CT scan.
  • Simple nephrectomy removes the whole kidney and the tumor. The kidney on the other side of the body will take over filtering blood and producing urine.
  • Radical nephrectomy removes the whole kidney with the tissues around it. Some lymph nodes in the area may also be removed.
  • Chemotherapy uses drugs to kill cancer cells. Chemotherapy may be taken by pill, or it may be put into the body by a needle in a vein or muscle. Chemotherapy is called a systemic treatment because the drugs enter the bloodstream, travel through the body, and can kill cancer cells throughout the body. Chemotherapy given after an operation to remove the tumor is called adjuvant therapy.

When very high doses of chemotherapy are used to kill cancer cells, these high doses can destroy the blood-forming tissue in the bones (the bone marrow). If very high doses of chemotherapy are needed to treat the cancer, bone marrow may be taken before therapy and stored frozen. Following high dose chemotherapy, the bone marrow is given back through a needle in a vein. This is called autologous bone marrow reinfusion and is only very rarely used for Wilms Tumor.

Radiation therapy uses x-rays or other high-energy rays to kill cancer cells and shrink tumors. Radiation for Wilms' tumor usually comes from a machine outside the body (external radiation therapy). Radiation may be used before or after surgery and/or chemotherapy.

Treatment of Wilms' tumor by stage

Treatments for Wilms' tumor depend on the stage of your child's disease, the tumor cell histology (cell type under the microscope, either "favorable" (85% of Wilms Tumors) or "unfavorable, anaplastic," 15% of Wilms Tumors), your child's age and general health.

Your child may receive treatment that is considered standard based on its effectiveness in patients in past clinical trials, or you may choose to have your child take part in a clinical trial. Clinical trials are designed to test potentially better treatments against treatment that is currently considered standard of care in hopes of finding better ways to treat cancer patients. Clinical trials are going on in most parts of the country for most stages of Wilms' tumor. The good news is that Children's Oncology Group clinical trials are closely overseen by a data monitoring committee, so that in real time, if one treatment is found to be better than another, the treating physicians are notified immediately, and your child's treatment will be changed right away if necessary.

Stage I Wilm's tumor

If you child has stage I Wilms' tumor, regardless of histology, the treatment will consist of surgery to remove the kidney and some surrounding lymph nodes followed by 18 weeks of chemotherapy. Regardless of histology, Stage I patients have an excellent prognosis.

Stage II Wilm's tumor

Your child's treatment depends on the histology of the cancer.

If your child has a favorable histology tumor, your child's treatment will probably be surgery to remove the cancer and some surrounding lymph nodes followed by chemotherapy.

If your child has an unfavorable histology tumor (anaplasia, clear cell sarcoma, or rhabdoid tumor of the kidney), your child's treatment will probably be surgery to remove the cancer followed by chemotherapy plus radiation therapy.

Stage III Wilm's tumor

Regardless of histology, your child's treatment will involve surgery to remove the cancer and some surrounding lymph nodes followed by chemotherapy and radiation therapy.

Sometimes the cancer cannot be removed during surgery because it is too close to important organs or blood vessels or because it is too large. In this case, the oncologic surgeon will only perform a biopsy. Chemotherapy with or without radiation therapy will be given to reduce tumor size. Once the cancer has become smaller, surgery can be performed, followed by additional chemotherapy and radiation therapy.

Stage IV Wilm's tumor

Your child's treatment will involve surgery to remove the cancer and surrounding lymph nodes followed by chemotherapy and radiation therapy to the abdomen. Radiation therapy to the lungs will be given if the cancer has also spread to the lungs.

Stage V Wilm's tumor

Both kidneys contain cancer. The oncologic surgeon will probably take out a piece of the cancer in both kidneys and remove some of the lymph nodes around the kidney to see whether they contain cancer. Following surgery, chemotherapy is given to shrink the cancer. A second operation is then performed to remove as much of the cancer as possible, while leaving as much of the kidneys as possible. Surgery will be followed by more chemotherapy and/or radiation therapy.

Recurrent Wilm's tumor

If your child's cancer comes back (recurs), treatment depends on the treatment he or she received before, how much time has passed since the first cancer was treated, the histology of the recurrent cancer, and where the cancer came back.

Depending on the above factors, your child's treatment may be surgery to remove the cancer, plus radiation therapy and chemotherapy.

Clinical trials are evaluating new treatments, such as new chemotherapy drugs and combinations, and very high doses of chemotherapy followed by bone marrow reinfusion.

Clear Cell Sarcoma of the Kidney

Clear cell sarcoma of the kidney is a primary kidney tumor, but not a type of Wilms' tumor. However, it is an important tumor with a significantly higher death rate than Wilms'.
The tumor can spread to lungs, bone, brain and soft tissues. If your child has clear cell sarcoma of the kidney, their treatment will probably be removal of the kidney followed by radiation therapy to the abdomen, radiation therapy to the lungs (if cancer is present there) and chemotherapy.

Rhabdoid Tumor of the Kidney

Rhabdoid tumor of the kidney is a distinctive, aggressive kidney cancer that grows and spreads quickly. It is usually seen in children younger than 1 year of age. These children usually have fever, blood in the urine and advanced stage cancer at diagnosis. The tumor has usually spread to the lungs or the brain. If you child has rhabdoid tumor of the kidney, their treatment will probably be removal of the kidney followed by chemotherapy. However, no satisfactory treatment has been developed as yet; the 4-year survival rate for all stages is approximately 25%.

Neuroepithelial Tumors of the Kidney

Neuroepithelial tumors of the kidney are rapidly growing kidney tumors that spread quickly. These tumors have usually spread to the outer kidney surface, veins that drain the kidney, or distant parts of the body at diagnosis. If your child has neuroepithelial tumor of the kidney, treatment according to Ewings' sarcoma/primitive neuroectodermal tumor treatment plan should be followed.

Cleveland Clinic Children's

Here at Cleveland Clinic Children's, we specialize in the care of children and young adults with cancer. We use a team approach that cares for all members of the family, recognizing that this is a very difficult time for all of them. Our goal is to have our patients get through therapy with as normal a life as possible, and to emerge from therapy knowledgeable about how to maintain their health.

Should you have more questions about the child or young adult in your life with cancer, please contact Cleveland Clinic Cancer Answer line at 1.866.223.8100. Your question will be forwarded to the Chair of the Pediatric Oncology Department.

We wish you and your child well.

Source: National Institutes of Health, National Cancer Institute, Children's Oncology Group

Health Information Home/Last Reviewed: 12/18/02 / Disclaimer & Privacy/ © Cleveland Clinic Health System 2002

This information is provided by the Cleveland Clinic Health System and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition.