Wilms' tumor (nephroblastoma) is a specific kind of kidney cancer.

• The cause of Wilms' tumor is not known, but some children may have a genetic abnormality.
• Children usually have a lump in the abdomen, and they may also have abdominal pain, fever, poor appetite, nausea, and vomiting.
• An imaging test is done to determine the nature and size of the lump.
• Treatment involves surgery and chemotherapy and sometimes radiation therapy.

Wilms' tumor usually develops in children younger than 5 years old, although it occasionally occurs in older children and rarely in adults. Very rarely, it develops before birth and appears in newborns. In about 4% of cases, Wilms' tumor occurs simultaneously in both kidneys.

The cause is not known, although a genetic abnormality may be involved in some cases. Wilms' tumor is more likely to develop in children with certain birth defects, for example, when both irises are missing or when one side of the body grows too much. Both of these defects may be caused by a genetic abnormality. However, most children with Wilms' tumor have no such recognizable abnormalities.

Symptoms

The first symptom is often a painless lump in the abdomen. The abdomen may enlarge, which parents may notice when children suddenly need a larger diaper size. Children may also have abdominal pain, fever, poor appetite, nausea, and vomiting. Blood appears in the urine in 15 to 20% of children. Because the kidneys are involved in controlling blood pressure, Wilms' tumor may cause high blood pressure.

This cancer can spread to other parts of the body, especially the lungs. If the lungs are involved, children may cough and be short of breath.

Diagnosis

Wilms' tumor is most often detected when parents notice a lump in the child's abdomen and take their child to a doctor. Or a doctor may feel such a lump during a routine examination. If the doctor suspects Wilms' tumor, ultrasonography, computed tomography (CT), or magnetic resonance imaging (MRI) is done to determine the nature and size of the lump.

Nephroblastoma

Prognosis

In general, Wilms' tumor is very curable. About 60 to 95% of children survive, depending on how widespread the cancer is. The outcome is usually better in children who are

• Younger
• Have smaller tumors
• Have a tumor that has not spread

Even older children and children with widespread tumors have a very good prognosis. However, one type of Wilms' tumor (which accounts for less than 5% of cases) is more resistant to treatment. Children with this type of tumor, which is recognized by examining a sample of the tumor under a microscope, have a poorer prognosis.

Treatment

Doctors treat Wilms' tumor by removing the kidney that contains the tumor. During the operation, the other kidney is examined to determine whether it also has a tumor. After surgery, doctors give the child chemotherapy drugs—most commonly actinomycinSome Trade Names
See Dactinomycin
D and vincristine. Other drugs such as doxorubicinSome Trade Names
DOXIL
, cyclophosphamideSome Trade Names
LYOPHILIZED CYTOXAN
, and etoposideSome Trade Names
VEPESID
are sometimes used. Children with larger or widespread tumors are also treated with radiation therapy.

Sometimes the tumor cannot be removed initially. In such cases, children are first treated with chemotherapy and radiation therapy to shrink the tumor. Then the tumor is removed.

Last full review/revision January 2009 by David N. Korones, MD