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Cancer Explained
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Wilms Tumor (Childhood Kidney Cancer)

A plain-language explanation of Wilms tumor, the most common kidney cancer in children, and how it is treated. Based on the National Cancer Institute.

NCI source

Last reviewed: 2026-07-07

The short answer

Wilms tumor is the most common kidney cancer in children and usually affects young children. It is often found as a swelling or lump in the belly. Most children are treated with surgery and chemotherapy, and outcomes are generally good.

  • Wilms tumor is the most common type of kidney cancer in children.

  • It usually affects young children, most often under age 5.

  • It is often first noticed as a firm, smooth lump or swelling in the abdomen.

  • Treatment usually includes surgery to remove the affected kidney plus chemotherapy.

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The full explanation.

The simple version

Wilms tumor is the most common kidney cancer in children. It usually affects young children, most often under age 5, and is frequently first noticed as a lump or swelling in the belly.

How it is found

Parents or doctors often first notice a firm, smooth lump or swelling in the child's abdomen. Other signs can include belly pain, fever, or blood in the urine. Imaging tests and, later, examination of the tumor confirm the diagnosis.

How it is treated

Treatment usually combines surgery to remove the affected kidney (a nephrectomy) with chemotherapy. Some children also receive radiation therapy, depending on the stage and the tumor's features. Most children do well with one healthy kidney.

The outlook

Outcomes for Wilms tumor are generally good, and treatment continues to improve through clinical trials. The stage of the tumor helps the team predict the outlook and plan treatment.

Most children with Wilms tumor do well with surgery and chemotherapy.

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Common questions

What is Wilms tumor?

Wilms tumor is the most common kidney cancer in children. It usually forms in one kidney but can sometimes affect both.

How is it usually found?

It is often first noticed as a firm, smooth lump or swelling in a child's belly, sometimes with abdominal pain, fever, or blood in the urine.

Who gets it?

It mainly affects young children, most often under age 5.

How is it treated?

Treatment usually includes surgery to remove the affected kidney, along with chemotherapy. Some children also receive radiation therapy depending on the stage and tumor features.

What is the outlook?

Outcomes for children with Wilms tumor are generally good. Your child's team can explain the outlook for their specific stage.

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  1. Q1.Wilms tumor is the most common cancer of which organ in children?
  2. Q2.How is Wilms tumor often first noticed?
  3. Q3.What is the usual treatment?
  4. Q4.How are outcomes for Wilms tumor generally described?

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Wilms Tumor (Childhood Kidney Cancer)