The kidneys are organs that filter waste products from the blood and create urine. Wilms' tumor (nephroblastoma) is a cancerous tumor of the kidney. It is thought to be caused by abnormal genes. The tumor may occur at any age, but it is most common in children 1 to 5 years of age.
Usually there are few early signs to suggest the tumor is present. Most children appear healthy. The most common sign is a swelling or mass in the abdomen. Often parents first find a mass while bathing or dressing their child.
Other signs and symptoms may include:
If a Wilms' tumor is strongly suspected, surgery will be done. The surgery is done for two reasons: 1) to remove as much of the tumor as possible; and 2) to get a piece of the tumor for examination (biopsy) under a microscope. A pathologist will look at the sample and decide if a definite diagnosis of Wilms' tumor can be made.
Tests used to evaluate patients with Wilms' tumor include blood tests, X-rays, CT scans and ultrasound scans of the abdomen (belly) (see Picture 1).
Picture 1: Having an ultrasound scan
Staging categories describe how far the tumor has spread. Staging is important because it helps decide the best treatment for the child. There are five stages of Wilms' tumor:
Tumor is limited to the kidney which has been completely removed during surgery. The child can function normally with one kidney.
Tumor extends past the kidney but is completely removed during surgery.
Tumor is left in the abdomen or in lymph nodes, or the tumor has ruptured. There is no evidence of spread beyond the abdomen.
Tumor has spread outside the abdomen, usually to the lungs or liver.
Tumor involves both kidneys.
Treatment of Wilms' tumor includes surgery, chemotherapy, and sometimes radiation therapy. The treatment chosen by the doctor depends on the stage.
Picture 2: The urinary system inside the body
If you have any questions or concerns, be sure to talk with your doctor or nurse.
Wilms' Tumor (PDF)
HH-I-133 6/90, Revised 10/14 Copyright 1990, Nationwide Children’s Hospital