Wilms’ tumor, also known as nephroblastoma, is a type of kidney cancer that primarily affects children. It can develop in one or both kidneys. It usually grows slowly.

Cancer occurs when abnormal cells in your body multiply uncontrollably. This can happen at any age, but some cancers are unique to childhood, and Wilms’ tumor is one of those: It’s typically diagnosed in children around 3 years of age. It’s uncommon after age 6, but it can occur in older children and adults.

While it’s relatively rare, it’s the fourth most common type of childhood cancer and most common type of childhood kidney cancer, affecting about one in every 10,000 children in the United States. Roughly 500 children are newly diagnosed each year.

Most kids show symptoms around the ages of 3 or 4, and these symptoms are similar to many other childhood ailments. That’s why it’s important to see your doctor for an accurate diagnosis.

Some symptoms include:

  • constipation
  • abdominal pain, swelling, or discomfort
  • nausea and vomiting
  • weakness
  • fatigue
  • loss of appetite
  • fever
  • blood in urine or discolored urine
  • high blood pressure (which can show up as chest pain, shortness of breath, and headaches)
  • increased and uneven growth of one side of their body

Doctors aren’t exactly sure what causes Wilms’ tumor. So far, researchers haven’t found any clear links between Wilms’ tumor and environmental factors, like drugs, chemicals, or infectious agents, either during a mother’s pregnancy or after birth.

However, there are a few things that researchers believe could be risk factors.

Genetic factors

Researchers don’t think children directly inherit the condition from their parents. Only about 1 percent of children with Wilms’ tumors have a relative who has had the same condition and usually, that relative isn’t a parent.

However, researchers believe certain genetic factors might increase a child’s risk or predispose children to develop Wilms’ tumor.

This is because kids with Wilms’ tumor often have mutations in certain genes, including the WT1 gene, the CTNNB1 gene, or the AMER1 gene — three genes that help the body make proteins and manage cell growth.

The following genetic syndromes might also increase a child’s risk for Wilms’ tumor:

Frasier syndrome, WAGR syndrome, and Denys-Drash syndrome are linked to changes or mutations in the WT1 gene. Beckwith-Wiedemann syndrome, a growth disorder that causes body and organ enlargement, is linked to a mutation in the WT2 gene.

These are both genes that suppress tumors and are found on chromosome 11. However, changes in these genes only account for a small percentage of Wilms’ tumors. There are likely other gene mutations that haven’t yet been discovered.

Children with certain development irregularities may also be more likely to have Wilms’ tumor. The following conditions are associated with the condition:

  • aniridia, which is when a child has a missing or partially missing iris
  • hemihypertrophy, which is when one side of the body is larger than the other
  • cryptorchidism, or undescended testicles
  • hypospadias, which is when the urinary opening is on the underside of the penis


According to the American Cancer Society, Wilms’ tumor occurs slightly more often in African-American children than in white children. It occurs least often in Asian-American children.


The risk of developing Wilms’ tumor appears to also be more common in children assigned female at birth.

Children who have any syndromes or birth irregularities linked to Wilms’ tumor should be regularly screened for the disease with physical exams and abdominal ultrasounds to look for any kidney tumors. Early detection can prevent the tumor from spreading from the kidney to other organs.

That’s why doctors usually recommend that children with a higher risk of Wilms’ tumor get an exam every 3 or 4 months until they’re about 8 years old.

You should also talk with your child’s pediatrician if you have any family members who have had Wilms’ tumor — they might want to schedule regular screenings in this case, too.

However, since the condition is extremely rare in children who don’t have any risk factors, children aren’t regularly screened for Wilms’ tumor unless they have symptoms, such as swelling in the abdomen.

In addition to an ultrasound, your child’s pediatrician may order other diagnostic tests to make an accurate diagnosis, including:

In some cases, they may do a chest X-ray to look for metastases (such as signs that cancer has spread to the lungs).

Once diagnosed, more tests will be done to determine how advanced the disease is.


Wilms’ tumor has five stages:

  • Stage 1: The tumor is contained within one kidney and can be completely removed with surgery. About 40 to 45 percent of Wilms’ tumors are stage 1.
  • Stage 2: The tumor has spread into the tissue and vessels around the kidney, but it can still be completely removed with surgery. About 20 percent of Wilms’ tumors are stage 2.
  • Stage 3: The tumor can’t be completely removed with surgery, and some cancer remains in the abdomen. About 20 to 25 percent of Wilms’ tumors are stage 3.
  • Stage 4: The cancer has spread to faraway organs, such as the lungs, liver, or brain. About 10 percent of Wilms’ tumors are stage 4.
  • Stage 5: The tumor is in both kidneys at the time of diagnosis. About 5 percent of Wilms’ tumors are stage 5.


Wilms’ tumors can also be classified by looking at the tumor cells under a microscope. This process is called histology.

Unfavorable histology

Unfavorable histology means that the tumors have a nucleus in the cells that looks very large and distorted. This is referred to as anaplasia. The more anaplasia, the harder the tumor is to cure.

Favorable histology

Favorable histology means that there is significantly less anaplasia. Over 90 percent of Wilms’ tumors have favorable histology. This means that most tumors are easier to cure.

Since this type of cancer is so rare, children with Wilms’ tumors are usually treated by a team of doctors, including:

  • pediatricians
  • surgeons
  • urologists (urinary tract specialists)
  • oncologists (cancer specialists)

The team of doctors will come up with a treatment plan for your child. Be sure to discuss all options available for your child as well as their possible side effects.

The main types of treatment are:

Most children undergo a combination of treatments. Surgery is usually the first treatment used for people in the United States. The goal of surgery is to remove the tumor.

In some cases, the tumor can’t be removed because it’s too big, or the cancer may have spread to both kidneys or into the blood vessels. If so, your doctors might first use chemotherapy or radiation therapy (or both) to try to shrink the tumor before surgery.

Your child might have to undergo more chemotherapy, radiation therapy, or surgery if the tumor isn’t completely removed the first time. The specific drugs and the extent of the treatment prescribed will vary depending on your child’s condition.

Clinical trials

Clinical trials are research studies that test out new treatments or procedures or test new combinations of established treatments. They’re a great way for doctors and people to learn better methods to treat cancer, especially rare cancers.

Ask your doctor if a local hospital conducts clinical trials to see whether you qualify.

As with any cancer, the spreading of the disease to other organs, or metastasis, is a potentially serious complication. If your child’s cancer spreads to distant organs, it will require more aggressive treatment, including chemotherapy.

Depending on the drugs used for chemotherapy, your child may also experience unpleasant side effects. These vary from child to child but may include:

  • hair loss
  • nausea and vomiting
  • fatigue
  • diarrhea
  • anemia
  • loss of appetite
  • weight loss
  • pain
  • neutropenia
  • mouth sores
  • bruising
  • sleep problems
  • bladder issues
  • skin and nail changes
  • increased risk of infection

Talk with your doctor about what to expect during and after your child’s treatment. Your doctor may prescribe additional medications to deal with the side effects of treatment. Hair will normally grow back within a few months after treatment is completed.

High blood pressure and kidney damage can occur as a result of your child’s tumor or its treatment. For this reason, follow-up care is just as important as the initial treatment.

Follow-up care may include physical exams and imaging tests to make sure the tumor hasn’t come back. It may also include blood and urine tests to check how the kidneys are working.

Ask your child’s doctor about long-term complications and how to look out for these problems.

About 90 percent of children with Wilms’ tumor survive, though the exact survival rate depends on the stage and histology of the tumor. The outlook for children with unfavorable histology is much worse than for children with favorable histology.

The 4-year survival rates by tumor stage and histology are as follows:

Favorable histology

  • Stage 1: 95–100 percent
  • Stage 2: 95–100 percent
  • Stage 3: 95–100 percent
  • Stage 4: 85–90 percent
  • Stage 5: 95–100 percent

Unfavorable histology

  • Stage 1: 75–90 percent
  • Stage 2: 80–85 percent
  • Stage 3: 50–90 percent
  • Stage 4: 30–75 percent
  • Stage 5: 65–100 percent

There’s a long-term risk that cancer will come back. This happens in 15 to 50 percent of the cases, depending on the stage and histology of the original tumor. The prognosis tends to be worse for those whose cancer recurs.

Wilms’ tumor can’t be prevented, which is why children with a family history of the condition or risk factors, such as birth irregularities or syndromes, should have frequent kidney ultrasounds. These screening tools can ensure early detection — which gives doctors the best chances of treating it quickly and effectively.

Talk with your child’s team of doctors and specialists for information and support. They can point you to other support resources available to you while your child goes through treatment. These resources can include:

  • social work services
  • counseling
  • support groups (online or in-person)
  • financial aid
  • advice on nutrition and diet

Ask to speak to parents who have already gone through treatment for Wilms’ tumor. They can provide additional support and encouragement.

You can also contact the American Cancer Society’s National Cancer Information Center at 800-227-2345. They have specialists on-call every day, 24 hours a day, to help you and your child during and after treatment.

Your child will be going through a lot during this time. You can make things a little bit easier for them by trying the following suggestions:

  • Stay with your child during treatment.
  • Bring a favorite toy or book with you to the hospital.
  • Make time for play while in the hospital, but make sure your child is getting adequate rest.
  • Make sure your child is eating and drinking enough.
  • Prepare your child’s favorite foods and increase their intake of nutritional fluids if their appetite is low.
  • Keep a journal or record of how your child is feeling at home so you can share it with your doctor.
  • Discuss the disease with your child in terms they can understand and encourage your child to share their feelings.
  • Try to make life as normal as possible for them.