Stages of Wilms Tumor

Wilms 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. The results of the tests and procedures done to diagnose and stage Wilms tumor are used to help make decisions about treatment.

There is no staging for the other types of childhood kidney tumors. The treatment of these tumors depends on the tumor type.

The following tests may be done to see if cancer has spread to other places in the body:

• Lymph node biopsy: The removal of all or part of a lymph node in the abdomen. A pathologist views the lymph node tissue under a microscope to check for cancer cells. This procedure is also called lymphadenectomy or lymph node dissection.
• Liver function test: A procedure in which a blood sample is checked to measure the amounts of certain substances released into the blood by the liver. A higher than normal amount of a substance can be a sign that the liver is not working as it should.
• 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, such as the chest.
• CT scan (CAT scan): A procedure that makes a series of detailed pictures of areas inside the body, such as the abdomen, pelvis, chest, and brain, taken from different angles. The pictures are made by a computer linked to an x-ray machine. A dye is 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.
• PET-CT scan: A procedure that combines the pictures from a positron emission tomography (PET) scan and a computed tomography (CT) scan. The PET and CT scans are done at the same time on the same machine. The pictures from both scans are combined to make a more detailed picture than either test would make by itself. A PET scan is a procedure to find malignant tumor cells in the body. A small amount of radioactive glucose (sugar) is injected into a vein. The PET scanner rotates around the body and makes a picture of where glucose is being used in the body. Malignant tumor cells show up brighter in the picture because they are more active and take up more glucose than normal cells do.
• 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 abdomen, pelvis, and 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 with cancer 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.
• Cystoscopy: A procedure to look inside the bladder and urethra to check for abnormal areas. A cystoscope is inserted through the urethra into the bladder. A cystoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a tool to remove tissue samples, which are checked under a microscope for signs of cancer.

There are three ways that cancer spreads in the body.

Cancer can spread through tissue, the lymph system, and the blood:

• Tissue. The cancer spreads from where it began by growing into nearby areas.
• Lymph system. The cancer spreads from where it began by getting into the lymph system. The cancer travels through the lymph vessels to other parts of the body.
• Blood. The cancer spreads from where it began by getting into the blood. The cancer travels through the blood vessels to other parts of the body.

Cancer may spread from where it began to other parts of the body.

When cancer spreads to another part of the body, it is called metastasis. Cancer cells break away from where they began (the primary tumor) and travel through the lymph system or blood.

• Lymph system. The cancer gets into the lymph system, travels through the lymph vessels, and forms a tumor (metastatic tumor) in another part of the body.
• Blood. The cancer gets into the blood, travels through the blood vessels, and forms a tumor (metastatic tumor) in another part of the body.

The metastatic tumor is the same type of cancer as the primary tumor. For example, if Wilms tumor spreads to the lung, the cancer cells in the lung are actually Wilms tumor cells. The disease is metastatic Wilms tumor, not lung cancer.

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 anaplastic tumors. Tumor cells that are anaplastic divide quickly and under a microscope 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 in the renal sinus (the part of the kidney where it joins the ureter) or to the lymph nodes.
• No cancer cells were found at the edges of the area where the tumor was removed.
• The outer layer of the kidney did not break open.
• The tumor did not break open.
• A biopsy was not done before 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. Cancer has not spread to lymph nodes. Before the tumor was removed, one of the following was true:

• Cancer had spread to the renal sinus (the part of the kidney where it joins the ureter).
• Cancer had spread to blood vessels outside the area of the kidney where urine is made, such as the renal sinus.

Stage III

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

• Cancer has spread to lymph nodes in the abdomen or pelvis (the part of the body between the hips).
• Cancer has spread to or through the surface of the peritoneum (the tissue that lines the abdominal cavity and covers most organs in the abdomen).
• A biopsy of the tumor was done before it was removed.
• The tumor broke open before or during surgery to remove it.
• The tumor was removed in more than one piece.
• Cancer cells are found at the edges of the area where the tumor was removed.
• The entire tumor could not be removed because important organs or tissues in the body would be damaged.

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 the abdomen and pelvis.

Stage V (bilateral)

In stage V (bilateral) Wilms tumor, cancer cells are found in both kidneys when the cancer is first diagnosed. The cancer in each kidney is staged separately as stage I, II, III, or IV.

Sometimes Wilms tumor and other childhood kidney tumors come back after treatment.

Childhood Wilms tumor may recur (come back) in the lungs, abdomen, liver, or other places in the body.

Childhood clear cell sarcoma of the kidney may recur in the brain, lungs, or other places in the body.

Childhood congenital mesoblastic nephroma may recur in the kidneys or in other places in the body.