Wilms Tumor

Wilms tumor is a rare kidney cancer that mainly affects children. Also known as nephroblastoma, it's the most common cancer of the kidneys in children, most often affecting children ages 3 to 4. It becomes much less common after age 5, but it can affect older children and even adults. 

Wilms tumor mostly occurs in just one kidney. But it can sometimes be in both kidneys at the same time. Over the years, progress in the diagnosis and treatment of Wilms tumor has greatly improved the prognosis for children with this disease. With treatment, the outlook for most children with Wilms tumor is good.

Types & Stages

There are two major types of Wilms tumors. These are grouped based on how they look under a microscope (called their histology):

• Favorable: The cancer cells in these tumors don’t look quite normal, but they don’t look very abnormal, either. Most Wilms tumors have a favorable histology. The chance of curing children with these tumors is very good.
   
• Anaplastic: In these tumors, the look of the cancer cells varies widely, and parts of the cell tend to be very large and distorted. This is called anaplasia. Anaplasia can be either focal (limited to just certain parts of the tumor) or diffuse (spread widely through the tumor).

Signs & Symptoms

Symptoms of Wilms tumor vary a lot. Some children don't seem to have any, but others have one or more of these symptoms:

• A mass in the stomach area that can be felt
• Swelling in the stomach area
• Pain in the stomach area
• Fever
• Blood in the urine
• Low red blood cell level, also known as anemia
• High blood pressure

Make an appointment with your child's health care provider if you see symptoms that worry you. Wilms tumor is rare. So it's likely that something else is causing symptoms and it's important to check out any concerns.

Diagnosis

To diagnose Wilms tumor, a health care provider might take a family history and do the following:

• A physical exam. The provider will look for possible signs of Wilms tumor.
   
• Blood and urine tests. These lab tests can show how well the kidneys are working.
   
• Imaging tests. Tests that create images of the kidneys help find whether a child has a kidney tumor. Imaging tests may include ultrasound, CT scans or MRI and chest X-rays.

Treatment

Treatment for Wilms tumor usually involves surgery and chemotherapy. It sometimes includes radiation therapy. Treatments depend on the stage of the cancer. Because this type of cancer is rare, a good choice for your child’s care is Stony Brook Children's Hospital.

Treatment for Wilms tumor may begin with surgery to remove all or part of a kidney. Surgery also confirms the diagnosis. The tissue removed during surgery is sent to a lab to learn whether it's cancerous and what type of cancer is in the tumor. Surgery may include:

• Removing part of the kidney. Known as a partial nephrectomy, this involves removing the tumor and a small part of the kidney around it. This might be done if the cancer is very small or for a child who has only one working kidney.
   
• Removing the kidney and surrounding tissue. Known as a radical nephrectomy, this type of surgery also involves removing nearby lymph nodes, part of the ureter and sometimes the adrenal gland. The kidney that's left can take on the work of both kidneys.
   
• Removing all or part of both kidneys. If the cancer affects both kidneys, surgery involves removing as much cancer as possible from both. Sometimes, this means removing both kidneys. The child would then need kidney dialysis or a kidney transplant.

Other treatments can include chemotherapy or radiation therapy.

Causes & Risk Factors

It's not clear what causes Wilms tumor. Factors that may increase the risk of Wilms tumor include:

• Race and ethnicity. In North America and Europe, Black children have a slightly higher risk of getting Wilms tumor than do children of other races. Asian-American children appear to have a lower risk than children of other races.
   
• Having a family history of Wilms tumor. Having someone in the family who's had Wilms tumor increases the risk of getting the disease.
   
• Certain conditions present at birth, including, aniridia, the colored portion of the eye—the iris—forms only in part or not at all; and hemihypertrophy, which means one side of the body or a part of the body is larger than the other side.
   
• Wilms tumor can occur as part of rare syndromes, including:
   
  • WAGR syndrome, which includes Wilms tumor, aniridia, genital and urinary system problems, and intellectual disabilities. 
     
  • Denys-Drash syndrome, which includes Wilms tumor, kidney disease and male pseudohermaphroditism, in which a boy's genitals aren't clearly male.
     
  • Beckwith-Wiedemann syndrome in which a child tends to be much larger than what is typical, known as macrosomia. This syndrome might cause organs in the stomach area to jut into the base of the umbilical cord, a large tongue, large internal organs and ears that are formed unusually.

Screening

There are no blood tests or other tests that are useful in screening otherwise healthy children for Wilms tumors, which can be found earlier in some children with tests such as an ultrasound of the abdomen. Screening is very important for children who have syndromes or birth defects known to be linked to Wilms tumors.

For these children, most doctors recommend physical exams by a specialist and ultrasound exams of the kidneys on a regular basis (for example, about every 3 or 4 months at least until the age of 7). This testing can sometimes find kidney tumors when they are still small and have not yet spread to other organs.

If a person is known to have inherited a WT1 gene mutation, genetic testing can be done to see if they passed the mutation on to their children. This testing can be done even before birth.