Wilms' Tumor: Diagnosis & Staging

When Wilms' tumor is suspected, doctors use imaging tests to identify signs of a tumor in the kidney and tumor cells that may have spread beyond the organ. Wilms' tumors that spread within the abdomen can affect the kidney bed, blood vessels, lymph nodes, or liver. The most common location for Wilms' tumor to spread outside the abdomen is the lungs.

To diagnose the tumor, your child may receive an abdominal sonogram, which uses sound waves to produce images of internal structures, as well as chest x-rays and CT scans. CT scans may include the use of an intravenous or oral dye containing iodine, which can help produce clearer images of tumors in the kidney and abdomen.

In order to prevent cancerous cells from spilling out of the tumor into the abdominal cavity, which would make treatment more difficult, our doctors do not remove tumor tissue through a biopsy. Instead, a surgeon removes the entire kidney along with the complete tumor to accurately diagnose the disease. Our doctors can then examine the tumor cells under a microscope to determine their type. If your child has Wilms' tumor in both kidneys, each kidney will be evaluated and treated separately.

In 90 percent of children with Wilms' tumor, the tissue has a favorable histology, meaning that cells appear relatively normal under the microscope and the disease can be more easily cured. When the tumor has an unfavorable histology, the cancer cells appear deformed and are more difficult to treat.

Staging

After our doctors diagnose a child with Wilms' tumor, we determine the extent to which the disease has spread. This process is known as staging. We do this using the National Wilms' Tumor Study Group (NWTS) staging system.

Staging is an important step that can help doctors determine the most effective treatment approach for your child that will also preserve your child's quality of life as much as possible.

  • Stage I - Cancer is limited to the kidney and can be completely removed by surgery. Approximately 40 percent of Wilms' tumors are classified as stage I tumors.
  • Stage II - Cancer has spread to the areas surrounding the kidney and can be completely removed by surgery. Approximately 20 to 25 percent of tumors are classified as stage II.
  • Stage III - Cancer has spread to the areas surrounding the kidney, including blood vessels, lymph nodes, or other nearby organs, and cannot be completely removed by surgery. Approximately 20 to 25 percent of tumors are classified as stage III.
  • Stage IV - Cancer has spread beyond the area of the kidney into organs such as the lungs, liver, bone, and brain. Approximately 10 percent of tumors are classified as stage IV.
  • Stage V - Tumors are found in both kidneys. Each kidney is staged separately. Approximately 5 percent of tumors are classified as stage V.