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Wilms Tumor

(Wilms' Tumor; Nephroblastoma)

By John J. Gregory, Jr., MD

Wilms tumor is a specific kind of kidney cancer that occurs mainly in young children.

  • 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 5% of cases, Wilms tumor occurs simultaneously in both kidneys.

The cause of Wilms tumor is not known, although a lack of certain genes or another 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. Problems with the kidneys, genitals, and urinary tract are common also. These defects, as well as intellectual disability, may be caused by a genetic abnormality. However, most children with Wilms tumor have no such recognizable abnormalities.


The first symptom of Wilms tumor 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 some children. Because the kidneys are involved in controlling blood pressure, Wilms tumor may cause high blood pressure (hypertension).

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.


  • Ultrasonography, computed tomography (CT), or magnetic resonance imaging (MRI) of the abdomen

  • Often surgery to remove the tumor at the time of 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, CT, or MRI of the abdomen is done to determine the nature and size of the lump. CT or MRI can also help doctors determine whether the tumor has spread to nearby lymph nodes or the liver and determine if the other kidney is affected. The doctor also does CT of the chest to determine whether tumors have spread to the lungs.

Surgery to remove part or all of the kidney (nephrectomy) that contains the tumor is done in most children based on the results of the CT or MRI. Doctors then analyze the tumor to confirm that it is a Wilms tumor. During surgery, doctors also remove nearby lymph nodes in the abdomen and analyze them for cancer cells. Cancer that has spread to the lymph nodes may require different treatment than cancer that has not.


In general, Wilms tumor is very curable. If the tumor is only in the kidney, about 85% to 95% of children are cured. Even if the tumor has spread beyond the kidney, cure rates range from 60% to 90% depending on how abnormal the cancer cells appear during testing. In general, the outcome is usually better in children who

  • Are younger

  • Have cancer cells that are less abnormal when the tumor is examined under a microscope

  • Have a tumor that has not spread

However, there is one type of Wilms tumor (which accounts for less than 5% of cases) that is more resistant to treatment. Children with this type of tumor have a poorer prognosis.

Wilms tumor can return, typically within 2 years of diagnosis. Children whose cancer has returned can still be cured.


  • Surgery and chemotherapy

  • Sometimes radiation therapy

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 actinomycin D and vincristine and sometimes doxorubicin. If the cancer has spread significantly, children are also treated with radiation therapy.

Rarely the tumor is extremely large and cannot be removed initially or tumors are in both kidneys. In such cases, children are first treated with chemotherapy to shrink the tumor or tumors. Then the tumor or tumors are removed.

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