Key Points for This Section

Wilms tumors and other childhood kidney tumors are staged during surgery and with imaging tests. In addition to the stages, Wilms tumors are described by their histology. The following stages are used for both favorable histology and anaplastic Wilms tumors: Stage I Stage II Stage III Stage IV Stage V

Wilms tumors and other childhood kidney tumors are staged during surgery and with imaging tests.

The process used to find out if cancer has spread outside of the kidney to other parts of the body is called staging. The information gathered from the staging process determines the stage of the disease. It is important to know the stage in order to plan treatment.

For Wilms tumor, the stage is determined during the initial surgery and with the results from imaging tests. The following imaging tests may be done to see if cancer has spread to other places in the body:

• CT scan (CAT scan): A procedure that makes a series of detailed pictures of areas inside the body, such as the chest or brain, taken from different angles. The pictures are made by a computer linked to an x-ray machine. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography.
• X-ray of the chest and bones: An x-ray is a type of energy beam that can go through the body and onto film, making a picture of areas inside the body.
• MRI (magnetic resonance imaging): A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the body, such as the brain. This procedure is also called nuclear magnetic resonance imaging (NMRI).
• Bone scan: A procedure to check if there are rapidly dividing cells, such as cancer cells, in the bone. A very small amount of radioactive material is injected into a vein and travels through the bloodstream. The radioactive material collects in the bones and is detected by a scanner.
• Ultrasound exam: A procedure in which high-energy sound waves (ultrasound) are bounced off internal tissues or organs and make echoes. The echoes form a picture of body tissues called a sonogram. An ultrasound of the major heart vessels is done to stage Wilms tumor.

In addition to the stages, Wilms tumors are described by their histology.

The histology (how the cells look under a microscope) of the tumor affects the prognosis and the treatment of Wilms tumor. The histology may be favorable or anaplastic (unfavorable). Tumors with a favorable histology have a better prognosis and respond better to chemotherapy than those with anaplastic histology. Tumor cells that are anaplastic divide rapidly and do not look like the type of cells they came from. Anaplastic tumors are harder to treat with chemotherapy than other Wilms tumors at the same stage.

The following stages are used for both favorable histology and anaplastic Wilms tumors:

Stage I

In stage I, the tumor was completely removed by surgery and all of the following are true:

• Cancer was found only in the kidney and did not spread to blood vessels of the kidney.
• The outer layer of the kidney did not break open.
• The tumor did not break open.
• A biopsy of the tumor was not done.
• No cancer cells were found at the edges of the area where the tumor was removed.

Stage II

In stage II, the tumor was completely removed by surgery and no cancer cells were found at the edges of the area where the cancer was removed. Before the tumor was removed, one of the following was true:

• Cancer had spread out of the kidney to nearby soft tissue.
• Cancer had spread to blood vessels of the kidney.

Stage III

In stage III, cancer remains in the abdomen after surgery and at least one of the following is true:

• Cancer spread to lymph nodes in the abdomen or pelvis (the part of the body between the hips).
• Cancer spread to or through the surface of the peritoneum (the layer of tissue that lines the abdominal cavity and covers most organs in the abdomen).
• A biopsy of the tumor was done during surgery to remove it.
• The tumor broke open before or during surgery to remove it.
• The tumor was removed in more than one piece.

Stage IV

In stage IV, cancer has spread through the blood to organs such as the lungs, liver, bone, or brain, or to lymph nodes outside of the abdomen and pelvis.

Stage V

In stage V, cancer cells are found in both kidneys when the disease is first diagnosed. Each kidney will be staged separately as I, II, III, or IV.

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