What is Wilms tumor?

Wilms tumor (also called nephroblastoma) is a type of cancer that forms in the kidney. The kidneys are a pair of organs in the lower back on each side of the spine. They filter the blood by taking out the waste and water. The waste and water leave the body as pee (urine). Wilms tumor usually affects 1 kidney. But it can affect both in a small number of children. The tumor can spread (metastasize) to another part of the body, such as the lungs.

Wilms tumor forms in the kidney.

Who gets Wilms tumor?

Children at any age can get Wilms tumor, but kids younger than age 5 are affected most often. Wilms tumor isn't contagious. This means that your child can’t pass it to another person. Sometimes Wilms tumor is linked to other rare medical syndromes.

What causes Wilms tumor?

Wilms tumor occurs because abnormal cells grow in the kidney. These cells then form a tumor. What causes the abnormal growth of cells isn't fully known. But certain genetic changes, conditions, and birth defects have been shown to increase a child’s risk of Wilms tumor. Your child’s healthcare provider may be able to tell you more.

What are the symptoms of Wilms tumor?

Some common symptoms of Wilms tumor include a lump in the belly (abdomen), pain and swelling in the belly, and blood in the pee. Appetite loss, fever, headache, blood pressure changes, and weight loss are also possible. Your child may have had some of these symptoms, or other symptoms.

How is Wilms tumor diagnosed?

Your child’s healthcare provider examines your child. You'll be asked about your child’s health history. Your child may also have 1 or more of the following:

• Blood and urine tests. These look at blood counts and see how well certain organs are working.

• Imaging tests. These take detailed images of areas inside the body. These may include X-ray, CT scan, MRI scan, or ultrasound.

• Surgery. This is done to take out the tumor and see if it's cancer.

Staging and grading of Wilms tumor

Staging is the process that tells the size of the cancer and how much it has spread. Your child's healthcare provider uses exams and tests to find out the size of the cancer and where it is. They can also see if the cancer has grown into nearby areas, and if it has spread to other parts of your child's body. 

Grading is used to describe how abnormal the cancer cells look when seen through a microscope. The more abnormal the cells are, the faster they grow. Staging and grading help the healthcare team plan treatment for your child. They also help determine the likelihood of cure (prognosis). The process used for Wilms tumor takes into consideration:

• Location of the primary tumor

• If the tumor has spread outside of the kidney to nearby tissues and lymph nodes

• If the cancer has spread to the other kidney or other parts of the body

• How abnormal the cancer cells look under a microscope

The Children's Oncology Group staging system is commonly used in the U.S. and Canada to stage Wilms tumors. The stages are written as Roman numerals and can have a value of I through V (1 through 5). The different stage numbers refer to the tumor’s size and if and where it has spread. For instance, stage I is an early stage of cancer. So the tumor is only in the kidney where it started. And all of the tumor was removed with surgery. Stage V means the cancer is in both kidneys when it's first diagnosed. Your child’s healthcare provider can tell you more if needed. Talk with your child's provider if you have any questions about the stage of your child’s cancer.

How is Wilms tumor treated?

The goal of treatment is to destroy the cancer cells. The kind of treatment used depends on the type and stage of tumor your child has. Your child may need 1 or more of these treatments:

• Surgery. A procedure (called a nephrectomy) may be done to remove the kidney where the tumor is located. Or if 1 kidney was already removed, surgery may be done to remove as much tumor as possible from the remaining kidney (called a partial nephrectomy).

• Chemotherapy (chemo). This destroys cancer cells with powerful cancer-fighting medicines. Your child may have a combination of medicines. They are given through a small tube (IV or intravenous line) that’s usually put into a vein in the arm or chest. Or they may be given by mouth or injection. Sometimes chemo is given before surgery to shrink the size of the tumor (called neoadjuvant chemo).

• Radiation therapy. This can destroy cancer cells and shrink a tumor using strong X-rays. Radiation may be used before or after other treatments.

Supportive treatments

Supportive treatments help to protect a child from infection, prevent discomfort, and bring the body’s blood counts back to a healthy range. During your child’s treatment, they may be given antibiotics. These are medicines that help prevent and fight infection. Other medicines may also be given. These help ease the side effects caused by treatment, such as upset stomach (nausea), vomiting, and diarrhea. Your child may also get a blood transfusion to restore the blood cells. The blood cells can't grow because of the effects of treatment. For the blood transfusion, blood is taken from a donor and stored until the child is ready to get it.

What are the long-term concerns?

With treatment, Wilms tumor is often curable. But chemo and radiation may cause some problems, such as damage to certain organs. So your child’s health will need to be watched closely for life. This may include routine healthcare provider visits, blood tests, and imaging tests. Also ask the healthcare team if your child will need to take special safety measures to protect the remaining kidney. For instance, they may not be able to play contact sports. Also, treatment can cause fertility issues later in life. And it can cause a risk for other cancers to develop.

Coping

Getting a cancer diagnosis for your child is scary and confusing. Remember that you're not alone. Your child’s healthcare team will help guide you and your child during your child’s illness and care. You may also want to get information and support for yourself. This can help you cope with the changes cancer brings. Learning about your child's cancer and talking with others who also have a child with cancer may help you and your family cope. Ask your child’s healthcare team for a list of resources.