Wilms’ tumor is a rare kidney cancer that primarily affects children. Also known as nephroblastoma, it’s the most common cancer of the kidneys in children. Wilms’ tumor most often affects children ages 3 to 4 and becomes much less common after age 5.
Wilms’ tumor most often occurs in just one kidney, though it can sometimes be found in both kidneys at the same time.
Over the years, advancements in the diagnosis and treatment of Wilms’ tumor have greatly improved the outlook (prognosis) for children with this disease. With appropriate treatment, the outlook for most children with Wilms’ tumor is very good.
Signs and symptoms of Wilms’ tumor vary widely, and some children don’t show any obvious signs. But most children with Wilms’ tumor experience one or more of these signs and symptoms:
- An abdominal mass you can feel
- Abdominal swelling
- Abdominal pain
Other signs and symptoms may include:
- Blood in the urine
- Nausea or vomiting or both
- Loss of appetite
- Shortness of breath
- High blood pressure
When to see a doctor
Make an appointment with your child’s doctor if you notice any signs or symptoms that worry you. Wilms’ tumor is rare, so it’s much more likely that something else is causing symptoms, but it’s important to check out any concerns.
It’s not clear what causes Wilms’ tumor, but in rare cases, heredity may play a role.
Cancer begins when cells develop errors in their DNA. The errors allow the cells to grow and divide uncontrollably and to go on living when other cells would die. The accumulating cells form a tumor. In Wilms’ tumor, this process occurs in the kidney cells.
In rare cases, the errors in DNA that lead to Wilms’ tumor are passed from a parent to the child. In most cases, there is no known connection between parents and children that may lead to cancer.
Factors that may increase the risk of Wilms’ tumor include:
- African-American race. In the United States, African-American children have a slightly higher risk of developing Wilms’ tumor than children of other races. Asian-American children appear to have a lower risk than children of other races.
- Family history of Wilms’ tumor. If someone in your child’s family has had Wilms’ tumor, then your child has an increased risk of developing the disease.
Wilms’ tumor occurs more frequently in children with certain abnormalities or syndromes present at birth, including:
- Aniridia. In aniridia (an-ih-RID-e-uh), the iris — the colored portion of the eye — forms only partially or not at all.
- Hemihypertrophy. Hemihypertrophy (hem-e-hi-PUR-truh-fee) means one side of the body or a part of the body is noticeably larger than the other side.
Wilms’ tumor can occur as part of rare syndromes, including:
- WAGR syndrome. This syndrome includes Wilms’ tumor, aniridia, genital and urinary system abnormalities, and intellectual disabilities.
- Denys-Drash syndrome. This syndrome includes Wilms’ tumor, kidney disease and male pseudohermaphroditism (soo-do-her-MAF-roe-dit-iz-um), in which a boy is born with testicles but may exhibit female characteristics.
- Beckwith-Wiedemann syndrome. Children with this syndrome tend to be significantly larger than average (macrosomia). Other signs may include abdominal organs that jut out into the base of the umbilical cord, a large tongue (macroglossia), enlarged internal organs and ear abnormalities. There is also an increased risk of tumors, including a type of liver cancer called hepatoblastoma.
Wilms’ tumor can’t be prevented by anything you or your child can do.
If your child has risk factors for Wilms’ tumor (such as known associated syndromes), the doctor may recommend periodic kidney ultrasounds to look for kidney abnormalities. Although this screening can’t prevent Wilms’ tumor, it may help detect the disease at an early stage.
To diagnose Wilms’ tumor, your child’s doctor may recommend:
- A physical exam. The doctor will look for possible signs of Wilms’ tumor.
- Blood and urine tests. These lab tests can’t detect Wilms’ tumor, but they can indicate how well the kidneys are working and uncover certain kidney problems or low blood counts.
- Imaging tests. Tests that create images of the kidneys help the doctor determine whether your child has a kidney tumor. Imaging tests may include an ultrasound, computerized tomography (CT) or magnetic resonance imaging (MRI).
Once your child’s doctor diagnoses Wilms’ tumor, he or she works to determine the extent (stage) of the cancer. The doctor may recommend a chest X-ray or chest CT scan and bone scan to determine whether the cancer has spread beyond the kidneys.
The doctor assigns a stage to the cancer, which helps determine the treatment options. In the United States, guidelines developed through the National Wilms Tumor Study of the Children’s Oncology Group include these five stages:
- Stage I. The cancer is found only in one kidney, is completely contained within the kidney, and can be completely removed with surgery.
- Stage II. The cancer has spread to the tissues and structures beyond the affected kidney, such as nearby fat or blood vessels, but it can still be completely removed by surgery.
- Stage III. The cancer has spread beyond the kidney area to nearby lymph nodes or other structures within the abdomen, the tumor may spill within the abdomen before or during surgery, or it may not be completely removed by surgery.
- Stage IV. The cancer has spread outside the kidney to distant structures, such as the lungs, liver, bones or brain.
- Stage V. Cancer cells are found in both kidneys (bilateral tumors).