What is Wilms’ tumor?

Wilms’ tumor is a rare type of kidney cancer that primarily affects children. About one in every 10,000 children is affected by Wilms’ tumor in the United States. Roughly 500 children are newly diagnosed each year. Although rare, Wilms’ tumor is the most common type of kidney cancer in children, and the fourth most common type of childhood cancer overall.

Cancer occurs when abnormal cells in your body multiply uncontrollably. This can happen at any age, but some cancers are unique to childhood. Wilms’ tumor, also known as nephroblastoma, is one such cancer.

Wilms’ tumor is typically diagnosed in children around 3 years of age. It’s uncommon after age 6, but it can occur in older children and adults.

Wilms’ tumor most often occurs in children with an average age of 3 to 4 years. Symptoms of are similar to those of other childhood ailments, so it’s important to see your doctor for an accurate diagnosis. Children with Wilms’ tumor might display the following symptoms:

  • constipation
  • abdominal pain, swelling, or discomfort
  • nausea and vomiting
  • weakness and fatigue
  • loss of appetite
  • fever
  • blood in their urine or discoloration of their urine
  • high blood pressure, which may cause chest pain, shortness of breath, and headaches
  • increased and uneven growth of one side of their body

It’s not clear what exactly causes Wilms’ tumors. So far, researchers haven’t found any clear links between Wilms’ tumor and environmental factors. These factors include drugs, chemicals, or infectious agents, either during a mother’s pregnancy or after birth.

Genetic factors

Researchers don’t think children directly inherit the condition from their parents. Only one to two percent of children with Wilms’ tumors have a relative who has had the same condition. That relative typically isn’t a parent.

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

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

  • Beckwith-Wiedemann syndrome
  • WAGR syndrome
  • Denys-Drash syndrome
  • Frasier syndrome
  • Perlman syndrome
  • Sotos syndrome
  • Simpson-Golabi-Behmel syndrome
  • Bloom syndrome
  • Li-Fraumeni syndrome
  • Trisomy 18, also called Edward’s Syndrome

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 birth defects may be more likely to have Wilms’ tumor. The following birth defects are associated with the condition:

  • aniridia: a missing or partially missing iris
  • hemihypertrophy: when one side of the body is larger than the other
  • cryptorchidism: undescended testicles in boys
  • hypospadias: when the urinary opening is on the underside of the penis


Wilms’ tumor occurs slightly more often in African-American children than in white children. It’s least common in Asian-American children.


The risk for development of Wilms’ tumor may be higher in females.

Children who have any syndromes or birth defects linked to Wilms’ tumor should be screened for the disease. These children should have a physical exam and an ultrasound on a regular basis. The ultrasound will look for any kidney tumors before the tumor spreads to other organs.

According to the American Cancer Society, doctors recommend that children with a higher risk of Wilms’ tumor get an exam every three or four months until they’re about 8 years old. Talk to your doctor if you have any family members who have had Wilms’ tumor. If you do, your doctor may recommend that all children in your family have regular ultrasound tests.

The condition is extremely rare in children who don’t have any risk factors. Therefore, tests for Wilms’ tumor aren’t typically done unless a child has symptoms, such as swelling in the abdomen.

To confirm a diagnosis of Wilms’ tumor, your doctor may order diagnostic tests, including:

These tests will help your doctor make an accurate diagnosis. Once diagnosed, more tests will be done to determine how advanced the disease is. Treatment and outlook will depend on the stage of your child’s cancer.


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 no anaplasia. Over 90 percent of Wilms’ tumors have favorable histology. This means 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 or urinary tract specialists
  • oncologists, or 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:

  • surgery
  • chemotherapy
  • radiation therapy

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. They are 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 if 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.

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 to 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 are cured. 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 four-year survival rates by tumor stage and histology are as follows:

Favorable histology

– Stage 1: 99 percent

– Stage 2: 98 percent

– Stage 3: 94 percent

– Stage 4: 86 percent

– Stage 5: 87 percent

Unfavorable histology

– Stage 1: 83 percent

– Stage 2: 81 percent

– Stage 3: 72 percent

– Stage 4: 38 percent

– Stage 5: 55 percent

Wilms’ tumor can’t be prevented. Children with a family history of the condition or risk factors, such as birth defects or syndromes, should have frequent kidney ultrasounds. These screening tools can ensure early detection.

Talk with your child’s team of doctors and specialists for information and support. They can point you in the direction of 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