Pediatric Wilms tumor (nephroblastoma)

What are pediatric Wilms tumors (nephroblastoma)?

Wilms tumors are a type of kidney cancer that primarily affects children. Wilms tumor is the most common type of pediatric kidney cancer. These tumors usually occur before age 5 and are almost always detected by age 10.

Most children have one tumor in one kidney, but a small number of children develop multiple tumors in one or both kidneys. Wilms tumor is also called nephroblastoma.

What are the different types of pediatric Wilms tumors (nephroblastoma)?

Doctors classify Wilms tumors based on how cancer cells look under a microscope.

The two types of Wilms tumors are:

1. Favorable histology - These cancer cells look more like healthy cells than diseased ones. Nearly 90% of Wilms tumors have a favorable histology. This type is easier to treat and cure.

2. Anaplastic histology - Anaplastic cells look very different from healthy cells because their central parts, which contain DNA, are enlarged and distorted. This condition is called anaplasia. Diffuse anaplasia, or distortion throughout a tumor, is harder to treat than focal anaplasia, which is distortion found in just one part of the tumor.

What are the signs and symptoms of pediatric Wilms tumors (nephroblastoma)?

Wilms tumors can grow fairly large before you or your child notice symptoms. One of the first signs is abdominal swelling. Your child’s belly may look bloated or you might feel a hard lump when you press on the stomach. Some children have abdominal pain.

Other symptoms include:

• Blood in urine

• Constipation

• Fatigue

• Fever

• Loss of appetite and weight loss

• Nausea and vomiting

• Shortness of breath

How are pediatric Wilms tumors (nephroblastoma) diagnosed?

We may use one or more of the following tests to diagnose a Wilms tumor:

• Blood test - measure blood cell counts

• Urinalysis - assess kidney function

• CT scan (computed tomography) - to view cross-sectional images of organs and detect kidney tumors

• Magnetic Resonance Imaging (MRI) - to get detailed 3D images of organs and surrounding soft tissues. MRIs can help determine if a cancer has spread.

• Ultrasound - to view the kidney in 3D and look for tumors

What causes Wilms tumors (nephroblastoma) in children?

Most children develop Wilms tumors for no apparent reason. The disease is slightly more common in girls and black children.

Any child can get these tumors, but these factors increase their risk:

• Birth defects - An estimated one out of every 10 children with Wilms tumors also has a genetic condition present at birth (a birth defect). Certain pediatric chromosomal abnormalities and tumor-causing conditions like Beckwith-Wiedemann syndrome increase a child’s chances of Wilms tumors.

• Family history - Certain gene changes (genetic mutations) may slightly increase Wilms tumor risk. Up to 2% of children with Wilms tumors have a relative with the same cancer.

How are pediatric Wilms tumors (nephroblastoma) treated?

Surgery (nephrectomy)

Kidney surgery (nephrectomy) is the best way to treat Wilms tumors.

• Radical nephrectomy - We remove the entire kidney and tumor along with some nearby glands and fatty tissue. This approach ensures that none of the cancerous tissue remains. Having just one kidney shouldn’t affect your child’s health or lifespan.

• Partial nephrectomy (kidney-sparing surgery) - If both kidneys have tumors, we remove just the tumors and some of the surrounding tissue. The remaining kidney works almost as efficiently as a whole kidney and shouldn’t affect your child’s health or quality of life.

Follow up

• Chemotherapy - We may give chemotherapy before surgery to destroy the cancer cells and shrink the tumor (called neoadjuvant chemotherapy) or after surgery to get rid of lingering cancer cells.

• Radiation therapy - We may recommend using high-energy radiation beams to destroy cancer cells as part of the initial treatment of some Wilms tumor or in the rare cases where the tumor returns after treatment.

Why Children's Health?

At Children's Health, the surgeons are also faculty members at UT Southwestern Medical Center. They see more children with Wilms tumors than almost any other cancer center in the country. This gives them the experience to identify the surgical approach that is right for your child, and to make surgery as successful as possible.

Your child’s care team may include:

• Oncologists

• Oncology pharmacists

• Urologists

• Genetic counselors

• General surgeons

• Child life specialists

• Mental health counselors

• Social workers