Wilms Tumor

Wilms tumor, a type of tumor found mainly children, usually (but not always) forms on only one kidney. It’s almost always diagnosed before the age of 10. It’s a little more common in girls than boys.


A Wilms tumor is growing on a kidney near the ureter.
A Wilms tumor is a type of kidney tumor that most often affects children.

What is Wilms tumor?

Wilms tumor is a kidney tumor found almost always in children. This condition represents nearly 90% of kidney tumors in children. In some cases, Wilms tumor is part of a group of conditions that are present at birth. These are called congenital syndromes.

Wilms tumor is also called Wilms’ tumor or nephroblastoma. Usually, there is only one tumor on one kidney, but there can sometimes be tumors on both kidneys (bilateral) or more than one cancerous spot on one kidney.


Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

Who does Wilms tumor affect?

Although there’ve been rare cases in adults, Wilms tumor is a cancer found mostly in children under 15 years old. About 95% of cases of this disease are diagnosed by the time a child is 10 years old.

The risk is higher in Black children and lower in Asian children. Wilms tumor is a little bit more common in girls than boys.

Wilms tumor has been passed down in the genes of a very small percentage of families.

How common is this condition?

There are an estimated 500 new cases of Wilms tumor diagnosed in the U.S. every year.


What types of congenital (present at birth) syndromes are often found with Wilms tumor?

Very rarely, people with Wilms tumor also have other congenital syndromes. Some of these syndromes include:

  • Beckwith-Wiedemann syndrome: Children with this syndrome have a 5% to 10% risk of developing Wilms. This syndrome is classified as an overgrowth syndrome — body parts grow larger and one side of the body doesn’t always match the other side.
  • WAGR syndrome: Children with this syndrome have about a 50% chance of developing Wilms tumor. (The “W” in the name stands for Wilms.) Other complications include lack of an iris in the eye (Aniridia) and Genital or the Renal issues.
  • Denys-Drash syndrome (also known as Drash syndrome): Children with this grouping of medical conditions have a 90% chance of developing Wilms. Other issues involve their genitals and kidneys.

Symptoms and Causes

What are the signs and symptoms of Wilms tumor?

Signs and symptoms of Wilms tumor include:


What causes Wilms tumor?

Although a small number of people inherit a gene for Wilms tumor, we don’t really know what causes it.

Diagnosis and Tests

How is Wilms tumor diagnosed?

If you’ve found a lump near your baby’s diaper line, or you’ve had to move to bigger diapers because of the lump, your healthcare provider may decide to test for Wilms tumor. The tumors sometimes get quite big, even bigger than the kidney itself.

If your child has one of the syndromes or genetic issues associated with Wilms, you and your provider may decide to do regular testing.

Tests to diagnose Wilms tumor include:

  • A physical exam that includes pressing down carefully on your child's abdomen.
  • Imaging tests like abdominal ultrasound, CT scan – usually with contrast. Your provider might order an X-ray or CT scan of your child's chest to find out if cancer has spread (metastasized) to their lungs. Imaging tests can show if your child has a tumor. Your provider can also use the tests to tell the difference between Wilms tumor and other types of kidney cancer.
  • Laboratory tests of blood and urine, including liver function and blood clotting tests.
  • A biopsy, which means that tissue from the tumor is removed and sent to the laboratory for testing.

What should I know about staging and Wilms tumor?

There are two different ways to stage Wilms tumor. Staging is the name for the way that healthcare providers determine if and how far the cancer has spread beyond its original location. The higher the number, the farther the cancer has spread.

Throughout Europe, healthcare providers use the International Society of Paediatric Oncology (SIOP) staging system. In the U.S. and Canada, healthcare providers use the Children’s Oncology Group (COG) staging system.

One difference between the two systems is that the COG system uses surgery to stage the tumor before chemotherapy. The SIOP system uses surgery after chemotherapy to do the staging.

Under the COG system, staging is as follows:

  • A Stage I tumor is only in your child's kidney and is removed completely during surgery.
  • A Stage II tumor has grown past your child's kidney, but is also removed completely.
  • A Stage III tumor isn’t able to be removed completely and some tissue remains in your child's abdominal area.
  • A Stage IV tumor has grown beyond your child's abdomen and pelvis to places like their lungs, liver, bone or brain.
  • A Stage V tumor is bilateral, or present in both kidneys. Your provider will do staging on each kidney separately.

Management and Treatment

How is Wilms tumor treated?

Wilms tumor is almost always treated with a combination of surgery and chemotherapy. Sometimes, treatment will include radiation therapy.

Many children with low-risk tumors are treated with surgery alone if the tumor hasn’t spread and can be taken out completely. Sometimes, your child may be treated with chemotherapy before surgery to make the tumor smaller and surgery safer.

Most chemotherapy is given through a vein (intravenously or I.V.). It can happen on an outpatient basis or in a hospital.

Your child may have side effects from the chemotherapy or radiation. If so, be sure to tell your provider. There are things you can do or medicines your child can take to lessen side effects.


How can I prevent Wilms tumor?

There’s nothing you or your child can do to cause or prevent Wilms tumor.

Outlook / Prognosis

What is the outlook (prognosis) for someone with Wilms tumor?

The outlook for someone with Wilms tumor is generally good for almost all stages of Wilms tumor. It’s best when your healthcare provider is able to remove the tumor entirely and no cancer is found elsewhere in your child's body. There is a chance that Wilms tumor can come back (recur).

Is Wilms tumor deadly?

Although Wilms tumor can be treated successfully by a combination of surgery and chemotherapy and/or radiation, it’s still cancer. It can still be fatal.

What is the survival rate for Wilms tumor?

About 90% of people diagnosed with Wilms tumor are still alive five years later. The rates may be higher or lower depending on the stage and other factors like tumor size and how the cancer cells appear under a microscope (histology). At one point, children younger than 2 years old had a lower relapse rate, but age is less a factor today than it used to be.

Living With

When should I see my healthcare provider about Wilms tumor?

If your child is being treated for Wilms tumor, you should contact your healthcare provider with any concerns. You should watch especially for any type of new symptom or if something seems to be getting worse.

During treatment, your healthcare team will let you know what things you should watch for, such as signs of urinary tract infections. This may require a trip to the emergency room.

You’ll probably need to make regular follow-up visits to make sure your child is staying healthy. Your provider may suggest your child sees a nephrologist (kidney specialist) or urologist (urinary tract specialist).

How can I help to keep my child healthy after treatment for Wilms tumor?

Your child should:

  • Drink adequate liquids to help keep the kidneys working well.
  • Limit the use of drugs like aspirin, ibuprofen and naproxen. Talk with your child’s healthcare provider about which products are least likely to harm their kidneys.
  • Have regular blood pressure checks.

Additional Common Questions

Is Wilms tumor painful?

Wilms tumor can be painful in some cases.

What’s the difference between Wilms tumor (nephroblastoma) and neuroblastoma?

Although the two terms look similar, they refer to cancer that starts in two different kinds of cells. Nephroblastoma is kidney cancer. Neuroblastoma is a cancer that starts in nerve cells, often in the adrenal glands but may invade a kidney. Both types of cancer affect children and both may show up as swollen spots in the abdomen.

A note from Cleveland Clinic

If your child is diagnosed with Wilms tumor, your provider might suggest that you contact a medical center that is familiar with treating childhood cancers. In addition to being rare, Wilms tumor is very treatable. Your child may be able to take part in a clinical trial. Most children with Wilms tumor are involved in these. The clinical trials have been responsible for many of the advances in treating Wilms tumor. Be sure to follow your healthcare provider’s instructions on follow-up appointments and healthy behaviors.

Medically Reviewed

Last reviewed on 06/13/2022.

Learn more about our editorial process.

Call Appointment Center 866.320.4573
Questions 216.444.2200