Wilms tumor (also called nephroblastoma) is the most common type of kidney cancer in children younger than 15 years. In the United States, about 650 children are diagnosed with it each year, and most are between the ages of 2 and 5 years. Wilms tumor can occur in older adolescents and adults, but this is rare.
The kidneys are bean-shaped organs located on either side of the spine, above the waist. Their main job is to remove waste and extra fluids from the body to make urine:
Wilms tumor can affect one or both kidneys. It may spread to other parts of the body, such as the lungs, liver, bone, brain, or lymph nodes.
A rare type of Wilms tumor called cystic partially differentiated nephroblastoma is made of cysts and usually occurs in young children.
During fetal development, some kidney cells may not develop normally. These abnormal groups of kidney cells may remain in one or both kidneys after birth, and in some cases, may lead to nephroblastomatosis (also called diffuse hyperplastic perilobar nephroblastomatosis) or Wilms tumor. In nephroblastomatosis (a non-cancerous kidney condition), these abnormal groups of cells may grow in many places inside the kidney or make a thick layer around the kidney. These abnormal groups of cells most often occur in both kidneys. Although nephroblastomatosis is not cancer, it can develop into Wilms tumor if left untreated. If a child has one kidney removed because of Wilms tumor and doctors find nephroblastomatosis in the removed kidney, the child has a higher risk of Wilms tumor in the remaining kidney.
Wilms tumor is caused by certain changes to the way the kidney cells function, especially how they grow and divide into new cells. The exact cause of these changes is often unknown. Learn more about how cancer develops at What Is Cancer?
A risk factor is anything that increases the chance of getting a disease. Not every child with one or more of these risk factors will develop a kidney tumor. And it will develop in some children who don't have a known risk factor.
Wilms tumor may be part of a genetic syndrome that affects growth or development. A genetic syndrome is a set of signs and symptoms or conditions that occur together and is caused by certain changes in the genes. Certain conditions or environmental exposures can also increase your child's risk of developing Wilms tumor. The following have been linked to Wilms tumor:
Talk with your child's doctor if you think your child may be at risk.
Some children have a higher risk of Wilms tumor. Regular testing can help find cancer at an earlier stage and improve your child's chance of survival. If your child has a higher risk of Wilms tumor, they may have an abdominal ultrasound for Wilms tumor every 3 months until they are at least 8 years old. This test can find small Wilms tumors before symptoms occur.
Children with Beckwith-Wiedemann syndrome or hemihypertrophy are at risk of tumors in the liver, adrenal glands, and kidneys. These children may receive testing to find Wilms tumor before symptoms occur. The testing schedule may include:
Children with aniridia and a certain gene change may have an abdominal ultrasound every 3 months until age 8 years to look for Wilms tumor.
Some children are diagnosed with Wilms tumor in both kidneys at the same time. Wilms tumor may also occur in the second kidney after your child is successfully treated for Wilms tumor in one kidney. If your child is at risk of developing Wilms tumor in the second kidney, they should have an abdominal ultrasound every 3 months for up to 8 years to monitor for any new tumors.
Sometimes Wilms tumor causes symptoms. But sometimes a parent may notice a lump in their child's abdomen or notice that their child's stomach looks bigger than before. In some cases, a doctor finds the tumor during a routine check-up. It's important to check with your child's doctor if your child has:
These symptoms may also be caused by other problems. The only way to know is for your child to see a doctor.
If your child has symptoms that suggest Wilms tumor, the doctor will need to find out if these are due to cancer or another problem. The doctor will ask when the symptoms started and how often your child has been having them. The doctor will also ask about your child's personal and family medical history and do a physical exam. Depending on these results, they may recommend tests to find out if your child has Wilms tumor, and if so, its extent (stage).
The following tests may be used to diagnose Wilms tumor. The results of these tests will help plan treatment.
A biopsy may be done before your child has any treatment, after chemotherapy, or during surgery.
If your child is diagnosed with a Wilms tumor, you will be referred to a pediatric oncologist. This is a doctor who specializes in childhood cancers. They will recommend tests to determine the extent of the cancer. The cancer may only be in one spot, but sometimes it spreads to other parts of the body. The process of learning the extent of the cancer in the body is called staging. It is important to know the stage of the tumor to plan the best treatment.
The following tests and procedures may be used to determine the stage of the Wilms tumor:
You may want to get a second opinion to confirm your child's diagnosis and treatment plan. If you seek a second opinion, you will need to get medical test results and reports from the first doctor to share with the second doctor. The second doctor will review the genetic testing report, pathology report, slides, and scans. This doctor may agree with the first doctor, suggest changes to the treatment plan, or provide more information about your child's tumor.
To learn more about choosing a doctor and getting a second opinion, visit Finding Cancer Care. You can contact NCI's Cancer Information Service via chat, email, or phone (both in English and Spanish) for help finding a doctor or hospital that can provide a second opinion. For questions you might want to ask at your child's appointments, visit Questions to Ask Your Doctor About Cancer.
It is not always clear from the family medical history whether a child with Wilms tumor has an inherited condition that increased their risk. Genetic counseling can assess the likelihood that your child's cancer is inherited and whether genetic testing is needed. Genetic counselors and other specially trained health professionals can discuss your child's diagnosis and your family's medical history to help you understand the:
Genetic counselors can also help you cope with your child's genetic testing results, including how to discuss the results with family members. They can advise you about whether other members in your family should receive genetic testing.
Genetic counseling may be done if your child has:
To learn more, visit Genetic Testing for Inherited Cancer Risk.
Staging is the process of learning the extent of the cancer in the body. Sometimes cancer is only in the kidney. Or, it may have spread to other parts of the body.
Besides stages, Wilms tumors are described by their histology, which refers to how the cells look under a microscope. The histology affects the prognosis and the treatment of Wilms tumor.
The histology may be favorable or anaplastic (unfavorable):
In stage I, the tumor was completely removed by surgery and all of the following are true:
In stage II, the tumor was completely removed by surgery and no cancer cells were found at the edges of the area where the cancer was removed. Cancer has not spread to the lymph nodes. Before the tumor was removed, one of the following was also true:
In stage III, cancer remains in the abdomen after surgery and at least one of the following is true:
In stage IV, cancer has spread through the blood to other parts of the body such as the lungs, liver, bone, or brain, or to lymph nodes outside the abdomen and pelvis.
In stage V (bilateral) Wilms tumor, cancer cells are found in both kidneys when the cancer is first diagnosed. The cancer in each kidney is staged separately as stage I, II, III, or IV.
Recurrent Wilms tumor is cancer that has come back after it has been treated. If there are signs that the cancer has returned, your child will have tests to find out where the cancer is in your child's body and if it has spread.
The type of treatment that your child will have depends on whether the Wilms tumor came back in the kidney or came back in other places in the body, such as the lungs, abdomen, or liver.
Learn more about Treatment of recurrent Wilms tumor.
A pediatric oncologist, a doctor who specializes in treating children with cancer, oversees treatment of Wilms tumor. The pediatric oncologist works with other health care providers who are experts in treating children and specialize in certain areas of medicine. Other specialists may include:
There are different types of treatment for children and adolescents with Wilms tumor. You and your child's care team will work together to decide treatment. Many factors will be considered, such as:
The goal of treatment is to kill the cancer cells and decrease the risk of late effects from treatment.
Your child's treatment plan will include information about the cancer, the goals of treatment, treatment options, and possible side effects. It will be helpful to talk with your child's care team before treatment begins about what to expect. For help every step of the way, visit our booklet, Children with Cancer: A Guide for Parents.
Types of treatment your child might have include:
Children with Wilms tumor may have surgery to obtain a biopsy sample or to remove the cancer. There are two types of surgery used to treat Wilms tumors:
After the doctor removes all the cancer that can be seen at the time of the surgery, your child may have chemotherapy or radiation therapy to kill any cancer cells that are left.
Sometimes, the tumor cannot be removed because:
If the tumor cannot be removed, your child will have a biopsy first. Then, they will receive chemotherapy to reduce the size of the tumor to make surgery possible. The goal of this approach is to save as much healthy kidney tissue as possible and reduce problems after surgery. Chemotherapy given before surgery is called neoadjuvant chemotherapy.
Radiation therapy uses high-energy x-rays or other types of radiation to kill cancer cells or keep them from growing. Wilms tumor is treated with external beam radiation therapy. This type of therapy uses a machine outside the body to send radiation toward the area of the body with cancer. Radiation therapy may be given alone or with other treatments, such as chemotherapy.
Learn more about External Beam Radiation Therapy for Cancer and Radiation Therapy Side Effects.
Chemotherapy (also called chemo) uses drugs to stop the growth of cancer cells. Chemotherapy either kills the cells or stops them from dividing. Chemotherapy may be given alone or with other types of treatment, such as radiation therapy.
For children with Wilms tumor, chemotherapy is injected into a vein. When given this way, chemotherapy enters the bloodstream and can reach cancer cells throughout the body.
Chemotherapy drugs used alone or in combination to treat Wilms tumor include:
Other chemotherapy not listed here may also be used.
Chemotherapy may be given before or after surgery. Chemotherapy given after surgery to kill any cancer cells that remain is called adjuvant therapy.
Learn more about how chemotherapy works, how it is given, common side effects, and more at Chemotherapy to Treat Cancer.
Stem cell transplant (or stem cell rescue) is a procedure to replace the blood-forming stem cells that are destroyed when high doses of chemotherapy are given to kill cancer cells. Before high-dose chemotherapy, stem cells (immature blood cells) are removed from the blood or bone marrow of your child and are stored in a freezer. After your child completes chemotherapy, the frozen stem cells are thawed and given back to them through an infusion. These stem cells grow into new blood cells.
For some children, joining a clinical trial may be an option. There are different types of clinical trials for childhood cancer. For example, a treatment trial tests new treatments or new ways of using current treatments. Supportive care and palliative care trials look at ways to improve quality of life, especially for those who have side effects from cancer and its treatment.
You can use the clinical trial search to find NCI-supported cancer clinical trials accepting participants. The search allows you to filter trials based on the type of cancer, your child's age, and where the trials are being done. Clinical trials supported by other organizations can be found on the ClinicalTrials.gov website.
Learn more about clinical trials, including how to find and join one, at Clinical Trials Information for Patients and Caregivers.
Clinical trials have led to improvements in the treatment of Wilms tumor, including the number of children who are cured.
To learn more about the treatments listed below, visit Types of treatment for Wilms tumor.
Treatment of stage I Wilms tumor with favorable histology may include:
Treatment of stage I anaplastic Wilms tumor is nephrectomy with removal of lymph nodes, followed by combination chemotherapy and radiation therapy to the flank area (either side of the body between the ribs and hipbone).
Use our clinical trial search to find NCI-supported cancer clinical trials that are accepting patients. You can search for trials based on the type of cancer, the age of the patient, and where the trials are being done. General information about clinical trials is also available.
Treatment of stage II Wilms tumor with favorable histology is nephrectomy with removal of lymph nodes, followed by combination chemotherapy.
Treatment of stage II anaplastic Wilms tumor is nephrectomy with removal of lymph nodes, followed by radiation therapy to the abdomen and combination chemotherapy.
Use our clinical trial search to find NCI-supported cancer clinical trials that are accepting patients. You can search for trials based on the type of cancer, the age of the patient, and where the trials are being done. General information about clinical trials is also available.
Treatment of stage III Wilms tumor with favorable histology is nephrectomy with removal of lymph nodes, followed by radiation therapy to the abdomen and combination chemotherapy.
Treatment of stage III anaplastic Wilms tumor may include:
Use our clinical trial search to find NCI-supported cancer clinical trials that are accepting patients. You can search for trials based on the type of cancer, the age of the patient, and where the trials are being done. General information about clinical trials is also available.
Treatment of stage IV Wilms tumor with favorable histology may include:
Treatment of stage IV anaplastic Wilms tumor may include:
Use our clinical trial search to find NCI-supported cancer clinical trials that are accepting patients. You can search for trials based on the type of cancer, the age of the patient, and where the trials are being done. General information about clinical trials is also available.
Treatment of stage V Wilms tumor or bilateral Wilms tumor may be different for each child and may include:
If a kidney transplant is needed because of kidney problems, it is usually delayed until 1 to 2 years after treatment is completed and there are no signs of cancer.
Use our clinical trial search to find NCI-supported cancer clinical trials that are accepting patients. You can search for trials based on the type of cancer, the age of the patient, and where the trials are being done. General information about clinical trials is also available.
Treatment of cystic partially differentiated nephroblastoma is surgery that may be followed by chemotherapy.
To learn about the treatments listed below, visit Types of treatment for Wilms tumor.
Treatment of recurrent Wilms tumor may include:
Use our clinical trial search to find NCI-supported cancer clinical trials that are accepting patients. You can search for trials based on the type of cancer, the age of the patient, and where the trials are being done. General information about clinical trials is also available.
If your child has been diagnosed with Wilms tumor, you likely have questions about how serious the cancer is and your child's chances of survival. The likely outcome or course of a disease is called prognosis.
The prognosis for Wilms tumor depends on:
Newly diagnosed Wilms tumor with favorable histology can often be cured.
No two people are alike, and responses to treatment can vary greatly. Your child's care team is in the best position to talk with you about your child's prognosis.
Cancer treatments can cause side effects. Which side effects your child might have depends on the type of treatment they receive, the dose, and how their body reacts. Talk with your child's treatment team about which side effects to look for and ways to manage them.
To learn more about side effects that begin during treatment for cancer, visit Side Effects.
Problems from cancer treatment that begin 6 months or later after treatment and continue for months or years are called late effects. Late effects of cancer treatment may include:
Some late effects may be treated or controlled. It is important to talk with your child's doctors about the effects cancer treatment can have on your child. Learn more about Late Effects of Treatment for Childhood Cancer.
Children with Wilms tumor and related problems may be monitored for late effects involving the kidneys.
Clinical trials are being done to find out if lower doses of chemotherapy and radiation can be used to lessen the late effects of treatment without changing how well the treatment works.
As your child goes through treatment, they will have follow-up tests or check-ups. Some of the tests that were done to diagnose the cancer or to find out the stage of the cancer may be repeated. Some tests will be repeated to see how well the treatment is working. Decisions about whether to continue, change, or stop treatment may be based on the results of these tests.
Some of the tests will continue to be done for years after treatment has ended. The results of these tests can show if your child's condition has changed, the health of your child's kidney or other organs, or if the cancer has come back.
To learn more about follow-up tests, visit Tests to diagnose Wilms tumor.
When your child has cancer, every member of the family needs support. Taking care of yourself during this difficult time is important. Reach out to your child's treatment team and to people in your family and community for support. To learn more, visit Support for Families: Childhood Cancer and the booklet Children with Cancer: A Guide for Parents.
For more childhood cancer information and other general cancer resources, visit:
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PDQ® Pediatric Treatment Editorial Board. PDQ Wilms Tumor. Bethesda, MD: National Cancer Institute. Updated <MM/DD/YYYY>. Available at: https://www.cancer.gov/types/kidney/patient/wilms-treatment-pdq. Accessed <MM/DD/YYYY>. [PMID: 26389390]
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