Wilms' tumor is a type of kidney cancer that mainly affects children. In most cases, Wilms' tumor affects only one of the two kidneys.
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In the fetus, some of the cells that are supposed to grow into mature kidneys stay as fetal kidney cells. Clusters of these cells sometimes remain after birth. If they do not mature within three or four years, they may grow without control or order. A large mass of these cells may develop into a Wilms' tumor.
A small percentage of children with Wilms' tumors have inherited an abnormal gene from one parent. This gene increases the chance that kidney cells will turn into a Wilms' tumor. Some children have certain birth defects that increase their risk for Wilms' tumor. However, many children with Wilms' tumors do not have any known inherited gene changes or birth defects. Researchers do not know why these children have some kidney cells that do not mature properly.
A risk factor is something that increases your chance of getting a disease or condition. One risk factor for Wilms' tumor is having a family member with a Wilms' tumor. Also, certain birth defects increase the risk of a Wilms' tumor. These include:
Patients with these abnormalities should be regularly screened for Wilms’ tumor during childhood.
The first noticeable symptom is usually a large lump or hard mass in the abdomen. Other symptoms may include:
Wilms' tumors may grow larger without causing any pain or other symptoms.
The doctor will ask about your child’s symptoms and medical history. A physical exam will be done.
Your child's bodily fluids and tissues may be tested. This can be done with:
Images may be taken of your child's bodily structures. This can be done with:
Children who have risk factors for Wilms' tumor should have a physical exam with a specialist and an ultrasound every three months until age six or seven. This screening should be done even if they do not have symptoms. It can help find tumors while they are small and have not yet spread to other parts of the body.
Wilms' tumor can be cured in most children. The specific treatment depends on whether the cancer has spread beyond the kidney to other parts of the body. The process for determining this is called staging. It uses the results of the diagnostic tests. Tumor size, cell type, tumor type, and your child’s age and health are also considered in choosing treatment.
In general, most tumors are treated only with combinations of chemotherapy. Other tumors often require the addition of radiation therapy.
Treatment may include:
The main treatment for Wilms' tumor is a type of surgery called nephrectomy. This is the removal of the kidney with the tumor. The tissue around the kidney may also be removed, as well as some nearby lymph nodes. The remaining kidney will take care of all of the needed functions for the body.
Chemotherapy is the use of drugs to kill cancer cells. Chemotherapy can be given in many forms, including pill, injection, and through a tube called a catheter. The drugs enter the bloodstream and travel through the body destroying mostly cancer cells, but also some healthy cells.
Currently, there is no known way to prevent Wilms' tumor.
American Cancer Society
National Cancer Institute
Childhood Cancer Canada
Driskoll K, Isakoff M, et al. Update on pediatric genitourinary oncology. Curr Opin Urol. 2007;17(4):281-286.
Wilms tumor. EBSCO DynaMed website. Available at:
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Updated May 1, 2013. Accessed June 20, 2013.
Wilms tumor. Nemours' KidsHealth.org website. Available at:
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Updated March 2012. Accessed June 20, 2013.
Last reviewed May 2014 by Mohei Abouzied, MD
Last Updated: 5/28/2014