Wilms tumor is a type of kidney cancer. It’s mainly found in children. Most of the time, it’s found in one kidney, not both.
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Before birth, some of kidney cells don’t mature like they’re supposed to. After the baby is born, clusters of these cells are still there. If they do not mature within 3 to 4 years, they may grow without control or order. A large mass of these cells may grow into a Wilms tumor.
The chances of Wilms tumor are higher for:
Many children with Wilms tumors don’t have these problems. The cause of their kidney cells not maturing is unknown.
Wilms tumor may be first felt as a large mass in the belly. Other problems may include:
Wilms tumors may grow larger without causing pain or other problems.
You will be asked about your child’s symptoms and health history. During a physical exam, the doctor will look for signs of the syndromes listed above. These may point to a Wilms tumor.
The exam and test results will help find out the stage of cancer. Staging helps with planning. Wilms tumor is staged from 1-4. Stage 1 is a very localized cancer. Stage 4 is a spread to other parts of the body.
Wilms tumor can be cured in most children. The plan depends on the stage of cancer. Many times, different methods are used. These may include:
Surgery is done to remove as much cancer as possible. Nearby lymph nodes or other sites with cancer will also be removed. A nephrectomy may be:
Chemotherapy is the use of drugs to kill cancer cells. It may given by mouth, shots, or IV. The drugs enter the bloodstream and travel throughout the body.
This is the use of radiation to kill cancer cells and shrink tumors after surgery. External radiation therapy is aimed at a tumor from a source outside the body.
If you have Wilms tumor in your family, talk to your doctor about genetic testing before you start your own family. If your child is at high risk, talk to their doctor about screening. This may help find tumors early.
American Cancer Society
National Cancer Institute
Childhood Cancer Canada
Sick Kids—The Hospital for Sick Children
Driskoll K, Isakoff M, Ferrer F. Update on pediatric genitourinary oncology. Curr Opin Urol. 2007;17(4):281-286.
Wilms tumor. EBSCO DynaMed website. Available at:
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Accessed January 29, 2021.
Wilms tumor. Kids Health—Nemours Foundation website. Available at: https://kidshealth.org/en/parents/wilms.html. Accessed January 29, 2021.
Last reviewed September 2020 by
EBSCO Medical Review Board
Mohei Abouzied, MD, FACP
Last Updated: 1/29/2021