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.
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.
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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.
There are an estimated 500 new cases of Wilms tumor diagnosed in the U.S. every year.
Very rarely, people with Wilms tumor also have other congenital syndromes. Some of these syndromes include:
Signs and symptoms of Wilms tumor include:
Although a small number of people inherit a gene for Wilms tumor, we don’t really know what causes it.
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:
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:
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.
There’s nothing you or your child can do to cause or prevent 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).
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.
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.
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).
Your child should:
Wilms tumor can be painful in some cases.
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.
Last reviewed by a Cleveland Clinic medical professional on 06/13/2022.
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