Nephroblastoma (Wilms Tumor)
Nephroblastoma, commonly known as Wilms tumor, is the most common kidney cancer in children, typically appearing before the age of five and often first noticed as a painless lump in the abdomen.
Table of contents
- What is Nephroblastoma?
- Who is Affected by Nephroblastoma?
- Causes and Risk Factors
- Signs and Symptoms
- How is Nephroblastoma Diagnosed?
- Cancer Staging
- Treatment Options
- Outlook and Survival
- Related Medical Conditions
What is Nephroblastoma?
Nephroblastoma, also called Wilms tumor, is a rare type of kidney cancer that primarily affects children. It is the most common kidney cancer in children and the most common abdominal cancer in this age group, and it ranks as the fourth most common pediatric cancer overall.[1][2]
Wilms tumor, Wilms’ tumor
The kidneys are bean-shaped organs located on either side of the spine, above the waist. Their main job is to filter waste and extra fluids from the body to make urine. Nephroblastoma can affect one kidney (unilateral) or both kidneys (bilateral).[4] Most cases involve only one kidney, but about 5% of children have tumors in both kidneys.[2]
- Kidneys
- Urinary system
- Adrenal glands (may be affected)
The tumor can spread to other parts of the body, most commonly to the lungs and liver, but also to lymph nodes, bones, or the brain.[1][3] During fetal development, some kidney cells may not develop normally. These abnormal groups of kidney cells may remain in one or both kidneys after birth and, in some cases, may lead to Wilms tumor.[4]
Who is Affected by Nephroblastoma?
Nephroblastoma most often affects children ages 3 to 4. It becomes much less common after age 5, but it can affect older children and even adults, though adult cases are rare.[1][3] In the United States, approximately 500 to 650 new cases are diagnosed each year.[2][3][4]
About 95% of cases are diagnosed by the time a child is 10 years old.[3] The disease affects girls slightly more often than boys.[2][3] Nephroblastoma is more common in children of African and African American descent, while it is least common in children of East Asian heritage.[2]
Causes and Risk Factors
The exact cause of nephroblastoma is not precisely known, but it is believed to be due to genetic changes that affect the normal development of kidney cells during pregnancy. Cancer begins when cells develop changes in their DNA that cause them to grow and divide uncontrollably.[1][2]
Some genetic markers that have been associated with Wilms tumor include alterations in genes called WT1, CTNNB1, and WTX. These gene changes have been found in about one-third of all Wilms tumors. Other genes associated with the disease include TP53 and MYNC.[2]
In most cases, nephroblastoma occurs by chance with no family history of the disease. Only about 1% of children with Wilms tumor have a relative with the disease, who is typically not a parent.[2] However, having certain genetic conditions or birth defects can increase the risk of developing Wilms tumor.[1]
Some conditions that may be associated with an increased risk of nephroblastoma include:[3][4]
- WAGR syndrome (which includes Wilms tumor, aniridia or missing iris in the eye, abnormalities of the genital and urinary system, and mental developmental delays) – children with this syndrome have about a 50% chance of developing Wilms tumor
- Beckwith-Wiedemann syndrome (an overgrowth syndrome where body parts grow larger and one side of the body doesn’t always match the other) – children with this syndrome have a 5% to 10% risk of developing Wilms tumor
- Denys-Drash syndrome (also known as Drash syndrome) – children with this condition have a 90% chance of developing Wilms tumor and also have problems with their genitals and kidneys
- Frasier syndrome
Children with certain birth defects, such as problems with the penis or testicle, may also be at higher risk.[3] Additionally, conditions like hemihypertrophy (when one side of the body is larger than the other), aniridia, and various urological disorders like cryptorchidism, horseshoe kidney, and hypospadias are associated with the disease, although they likely do not play a direct role in causing the cancer.[2]
Signs and Symptoms
Symptoms of Wilms tumor vary considerably. Some children don’t seem to have any symptoms at all, while others experience one or more clear signs of illness.[1]
The most common symptom is a painless mass or lump in the abdomen that can be felt. Often, this lump is first discovered by a parent while bathing or dressing the child, or while changing diapers.[1][3] The tumors can sometimes grow quite large, even larger than the kidney itself.[3]
Other symptoms may include:[1][3]
- Swelling in the abdomen
- Pain in the abdomen
- Blood in the urine (called hematuria)
- Fever with no clear reason
- High blood pressure (called hypertension), which in turn may cause nosebleeds, headaches, or blood in the eye
- Low red blood cell level, also known as anemia
- Decreased appetite
- Weakness or tiredness
- Weight loss
- Constipation
If you notice a lump or swelling in your child’s abdomen, or if your child has any symptoms that worry you, make an appointment with your child’s healthcare provider right away. It’s important to check out any concerns, even though Wilms tumor is rare and symptoms may be caused by other, more common conditions.[1]
How is Nephroblastoma Diagnosed?
If your child’s healthcare provider suspects Wilms tumor, they will begin with a complete medical history and physical examination. During the physical exam, the provider will carefully press down on your child’s abdomen to feel for any masses. It’s important that the child is handled carefully before and during any tumor evaluation, as applying too much pressure could potentially cause the tumor to rupture and spread cancer cells to other tissues.[1][3]
If your child has one of the genetic syndromes associated with Wilms tumor, you and your provider may decide to do regular testing and screening.[3]
Several tests may be ordered to diagnose nephroblastoma:[3][9]
- Abdominal ultrasound – This test uses high-frequency sound waves to create pictures of internal organs and blood vessels. It can show the kidney, the tumor, and blood vessels of the kidney, and help determine if there are tumors in the other kidney or other parts of the abdomen
- CT scan (computed tomography) – This test uses a series of X-rays and a computer to make detailed images of the abdomen. CT scans are much more detailed than standard X-rays and can show if cancer has spread
- MRI (magnetic resonance imaging) – This test uses magnets, radio waves, and a computer to make detailed images of the body. It can show if cancer has spread to other parts of the body or if there are cancer cells in lymph nodes or other nearby organs
- Chest X-ray or chest CT scan – These tests can show if cancer has spread to the lungs
- Blood and urine tests – These laboratory tests provide information about kidney and liver function, blood clotting, and overall health
- Biopsy – In some cases, a small sample of tissue may be removed and examined under a microscope to confirm the diagnosis
Imaging tests can show if your child has a tumor and help healthcare providers tell the difference between Wilms tumor and other types of kidney cancer.[3]
Cancer Staging
After finding Wilms tumor, the healthcare team will recommend additional tests to determine if the cancer has spread beyond the kidneys. This process is called staging the cancer. The stage helps doctors decide on the best treatment approach.[9]
In the United States, the stages for Wilms tumor are:[9]
- Stage 1 – The cancer is found only in one kidney and surgery can remove it all
- Stage 2 – The cancer has spread beyond the kidney, such as to nearby fat or blood vessels, but surgery can still remove it all
- Stage 3 – The cancer has spread beyond the kidneys to nearby lymph nodes (small organs that fight infection). It might also have spread to other places within the abdomen. The cancer cells might spill within the abdomen before or during surgery, or surgery might not be able to remove all the cancer
- Stage 4 – The cancer has spread outside the kidney to other places in the body, such as the lungs, liver, bones, or brain
- Stage 5 – Cancer cells are found in both kidneys. The tumor in each kidney is staged by itself
Treatment Options
Treatment for nephroblastoma typically involves a combination of approaches. Pediatric oncologists (cancer doctors for children) and surgeons work together to provide the best care.[9]
The main treatment options include:
Surgery is almost always part of the treatment plan. The first step is usually an operation to remove the tumor. The most common procedure is called a radical nephrectomy, which removes the whole kidney, part of the tube connecting the kidney to the bladder (ureter), and sometimes nearby lymph nodes. In some cases, only part of the kidney is removed (partial nephrectomy) if the tumor is small or if both kidneys are affected.[1][9]
Chemotherapy uses powerful medicines to kill cancer cells. Most children with Wilms tumor receive chemotherapy as part of their treatment. These drugs can be given before surgery to shrink the tumor or after surgery to kill any remaining cancer cells.[1][9]
Radiation therapy uses high-energy beams to kill cancer cells. Some children with Wilms tumor need radiation therapy, particularly those with more advanced disease or tumors that have spread.[1]
Biologic therapy (also called immunotherapy) boosts the body’s own ability to fight cancer. This treatment approach may be used in certain cases.[1]
The specific treatment plan depends on several factors, including your child’s age, overall health, the type and location of the tumor, how far the disease has spread (the stage), your child’s tolerance for specific treatments, and the characteristics of the tumor itself.[9]
Outlook and Survival
Over the years, progress in the diagnosis and treatment of Wilms tumor has greatly improved the outlook for children with this disease. With appropriate treatment, the prognosis for most children with Wilms tumor is very good.[1]
For children younger than 20 years with Wilms tumor, the 5-year relative survival rate is 93%.[2] This means that 93 out of every 100 children diagnosed with Wilms tumor are alive five years after diagnosis. Wilms tumor is curable in most children with treatment.[1][3]
Several factors can affect a child’s prognosis, including the stage of the cancer at diagnosis, the type of cells found in the tumor (called histology), the child’s age, and certain genetic features of the tumor. A poorer prognosis has been linked to changes in the TP53 gene and with the loss of certain genetic material at specific chromosomes.[2]
Most children recover from Wilms tumor and go on to live long, healthy lives. However, children who have been treated for cancer require close monitoring because treatment side effects may persist or develop months or years after treatment ends.[2]
Related Medical Conditions
Nephroblastoma may occur alongside or be associated with certain other conditions:
- Aniridia (partial or complete absence of the iris in the eye)
- Hemihypertrophy (overgrowth of one side of the body)
- Cryptorchidism (undescended testicle)
- Hypospadias (abnormal opening of the urethra)
- Nephroblastomatosis (a non-cancerous kidney condition that can develop into Wilms tumor)
