Wilms' Tumor

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

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

The cause of Wilms' tumor is not known, although a genetic abnormality may be involved in some cases. Children with certain birth defects, such as absence of the irises or excessive growth of one side of the body, both of which may be caused by a genetic abnormality, have an increased risk of developing Wilms' tumor. However, most children with Wilms' tumor have no such recognizable abnormalities.

Symptoms and Diagnosis

Symptoms include a large abdomen (for example, a rapid change to a larger diaper size), abdominal pain, fever, poor appetite, nausea, and vomiting. Blood appears in the urine in 15 to 20% of cases. 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. Involvement of the lungs can lead to a cough and shortness of breath.

The first sign of Wilms' tumor, a painless mass in their child's abdomen, is most often noticed by the parents. A doctor is usually able to feel a lump (mass) in the child's abdomen. If the doctor suspects Wilms' tumor, ultrasound, computed tomography (CT), or magnetic resonance imaging (MRI) is performed to determine the nature and size of the lump.

Prognosis and Treatment

Younger children, children with smaller tumors, and children whose tumor has not spread tend to fare better. In general, Wilms' tumor is very curable; about 70 to 95% of children with Wilms' tumor survive, depending on how widespread the disease is. Even older children and children with widespread tumors have a very good prognosis. However, one particular type of Wilms' tumor (present in less than 5% of cases) is more resistant to treatment. Children with this type of tumor, which is recognized by its microscopic appearance, have a poorer prognosis.

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, vincristine, and doxorubicin. Children with larger or widespread tumors also receive radiation therapy. Sometimes the tumor cannot be removed initially; in that case, the child is first treated with chemotherapy and radiation, and the tumor is removed when it is smaller.