Wilms' Tumor (1)

What Is It?

Wilms' tumor, also called nephroblastoma, is the most common form of kidney cancer to affect children. Wilms' tumor develops when cancerous (malignant) kidney cells multiply out of control, and eventually form a firm, grayish or tan mass (tumor). This mass usually is smooth and fairly round. As it grows larger, Wilms' tumor changes the normal shape and appearance of the kidney. It also can destroy areas of normal kidney tissue, and can cause bleeding into the urine. In some cases, the tumor eventually grows so large that it becomes noticeable as a firm, smooth lump in a child's side or abdomen. Without proper treatment, Wilms' tumor has the potential to spread outside the kidney, most commonly to the lungs and the liver.

Wilms' tumor is uncommon. Only about 500 new cases are diagnosed in the United States each year. It accounts for 5 percent to 6 percent of all childhood cancers in the United States. Wilms' tumor is much more common in African-American children than in Caucasians or Asian-Americans, and it is slightly more common in girls than in boys. In most cases, the tumor affects only one area in one kidney. Occasionally, tumors will affect both kidneys or will occur in multiple areas inside the kidney.

Children with certain birth defects are more likely to develop Wilms' tumor. These birth defects include the absences of the irises of the eyes (aniridia) and excessive growth on one side of the body, called hemihypertrophy.

Symptoms

Symptoms of Wilms' tumor can include:

• A firm lump or swelling in the child's abdomen or side. Often, this lump does not cause pain or discomfort.
  
• Abdominal pain
  
• Vomiting
  
• Blood in the urine
  
• High blood pressure (hypertension), which is triggered when the tumor blocks the blood supply to the kidney
  

Wilms' tumor often is discovered when a parent notices a mass while bathing or dressing a child, most commonly a child who is about 3 years old.

Diagnosis

The doctor will review your child's symptoms and medical history and the mother's pregnancy history. If your child has obvious birth defects, the doctor will ask questions about your family's history of related problems, especially those involving the genitals or urinary tract. The doctor also will review your family history of Wilms' tumor and other types of cancer. This is particularly important if you have relatives who developed cancer at a very young age.

The doctor then will examine your child, paying special attention to his or her abdomen and genital area. This will be followed by basic blood and urine tests, an ultrasound, and a computed tomography (CT) scan or magnetic resonance imaging (MRI) scan of the abdomen.