What is Wilms’ tumor?

Wilms’ tumor, also known as nephroblastoma, is a common type of cancer that initiates in the kidneys of children.

Nine of every 10 childhood cancers are Wilms’ tumors, according to the American Cancer Society.

The malignancy is named after Max Wilms, a German physician who wrote one of the first research articles on this type of cancer in 1899.

Most cases of Wilms’ tumor are discovered before it metastasizes to other organs in the body. However, these tumors often are quite large — even larger than the kidney in some cases — when they are detected.

Types/subtypes

The majority of Wilms’ tumors affect one kidney, and they are known as unilateral. In 5% to 10% of cases, more than one tumor develops. Bilateral disease, in which tumors are present in both kidneys, occurs in approximately 5% of cases.

The histology of Wilms tumor is determined under a microscope and can be categorized as favorable or unfavorable. More than 90% of tumors are of favorable histology and the chance for cure is good. However, patients with unfavorable histology — known as anaplastic Wilms’ tumor — have large, distorted nuclei found in the cancer cells, and this type is more difficult to cure.

Risk factors, symptoms

The exact cause of Wilms’ tumor is not known. Yet, there are certain factors that place a child at risk. Most occur among children between the ages of 3 and 4 years. Girls are more likely than boys to develop Wilms’ tumor.

The risk for Wilms’ tumor is highest among black children and lowest among Asian-American children.

Most children with Wilms’ tumor do not have a family history of the condition; only 1% to 2% have a relative with the same malignancy.

Among children with a family history of Wilms’ tumor, researchers suggest there is an abnormal or missing gene within their chromosomes that they inherited from a parents However, in most cases, the relative with Wilms’ tumor is not a parent.

Although it is most common for a child to have only one affected kidney, those with a family history of Wilms’ tumor are at a small increased risk for bilateral disease.

Approximately 10% of children with Wilms’ tumor have a birth defect or syndrome that places them at higher risk for the cancer. Birth defects associated with Wilms’ tumor include aniridia, hemihypertrophy, cryptorchidism and hypospadias in boys. The syndromes associated with Wilms tumor include WAGR syndrome, Denys-Drash syndrome, Fraser syndrome and Beckwith-Wiedemann syndrome.

A common symptom of Wilms’ tumor is abdomen swelling. Although routine screening for Wilms’ tumor is not recommended in otherwise healthy children, children with syndromes or birth defects are at increased risk for the disease. Therefore, it is recommended for these children to receive routine physical exams and ultrasounds of the abdomen.

Treatment

The initial treatment for Wilms’ tumor in the United States often is surgery. A short course of chemotherapy before surgery is the preferred treatment in Europe. Data suggest no differences in outcomes between the two methods.

The majority of children will undergo more than one treatment type, including surgery, radiation therapy and chemotherapy.

Much of the progress in treatments for Wilms’ tumor can be attributed to the National Wilms Tumor Study Group, part of the Children’s Oncology Group. Treating children with Wilms’ tumor requires a team approach. The care team often consists of a pediatrician, a pediatric surgeon or pediatric urologist, a pediatric oncologist and a pediatric radiation oncologist.

Future research

Additional research is needed to continue treatment advances and increase cure rates in children with Wilms’ tumor. One of the primary goals of The Children’s Oncology Group is to improve upon treatments for and quality of life of these children.

Specifically, researchers continue to examine how alterations in certain genes lead to Wilms’ tumors and are associated with tumor aggressiveness. They are studying how to treat each child more effectively and safely by determining which children require more aggressive treatment and which do not. For example, children with Wilms’ tumors who have specific alterations on chromosomes 1 and 16 are more prone to cancer recurrence. Therefore, these children may benefit from more intense treatment.

Researchers also are assessing gene alterations that appear to have an association with the growth and spread of Wilms’ tumor cells, and newer chemotherapies are being tested in children with unfavorable histology.

Other investigations are analyzing the use of targeted therapies and the use of stem cell transplants to treat tumors that do not respond to standard treatments.

More information is available at these websites:

www.cancer.org/cancer/wilmstumor/detailedguide/wilms-tumor-what-is-wilms-tumor

www.cancer.gov/types/kidney/hp/wilms-treatment-pdq

childrensoncologygroup.org/index.php/in-treatment-for-kidneywilms-tumor

www.mayoclinic.org/diseases-conditions/wilms-tumor/basics/definition/CON-20043492