Wilms tumor is a kind of cancer of the kidney, also known as nephroblastoma, that mostly affects children. Some cases do appear in adults. Of all kidney cancers, Wilms tumors are the most common type occurring in children. Nonetheless, there are only about 500 cases diagnosed each year in the United States and the incidence is about one in one million for people under the age of 15.
About 75 percent of children who are diagnosed with Wilms tumor are otherwise healthy. Symptoms of the disease include a palpable mass in the abdomen that is often first detected during a doctor’s visit, or by a parent. Often, there is no pain and the child appears healthy in other ways. Pain in the abdomen can occur in some cases, along with blood in the urine, unexplained fever, high blood pressure and constipation.
In about 25 percent of cases, Wilms tumor is associated with a group of genetic disorders known as WAGR. These result from abnormalities to a specific gene, WT1. This gene is associated with WAGR and Denys-Drash syndrome and is located on chromosome 11p13. Denys-Drash syndrome is a very rare form of kidney dis-function separate from the symptoms of Wilms.
A second gene, WT2, is associated with the Beckwith-Wiedemann syndrome and is located on chromosome 11p15. Beckwith-Wiedemann sufferers have enlarged organs, tongue and head and are at greater risk of Wilms tumor kidney cancer.
Several other genes have been identified which appear connected to inherited Wilms tumor. Gene FWT1, which is located on chromosome 17q, and FWT2, located on chromosome 19q are also implicated in genetic cases of Wilms tumor.
Other conditions associated with WAGR syndrome include aniridia in which the iris in the eye is missing. Problems with the urinary tract that are present at birth, and varying degrees of mental retardation, are also associated with WAGR, as well as hemihypertrophy which results in enlargement of one side of the body over the other.
Most cases of WAGR and Wilms tumor are diagnosed in children under the age of five. Children over the age of eight are rarely diagnosed. It is a form of cancer that responds well to treatment and 90 percent of patients live for five years or more. Complete recovery often occurs. Wilms tumor is diagnosed using ultrasound followed by CT and MRI scans. Ninety five percent of the time it only affects one kidney and remains contained.
Wilms tumor is first treated by assessing the stage of the tumor. The exact course of treatment will depend on the stage of the tumor’s development. Removing the kidney, if only one is affected, is often part of the treatment. If both kidneys are affected, the diseased tissue is removed leaving the healthy part of the kidney intact.
Chemotherapy is often prescribed as a follow up treatment and sometimes radiation therapy is also used. If the tumor is detected and treated in its early stages, Wilms tumor has a high rate of survival and recovery. Prognosis is worse if the cancer has spread to lungs, brain or other organs.
People of African descent are at a somewhat higher risk of acquiring Wilms tumor than other ethnic groups. It is also somewhat more common in siblings and twins, strengthening the possibility of a genetic basis. However, a complete understanding of the heritability of Wilms tumors is still ongoing. Clinical trials involving new drugs for treatment of Wilms tumors are underway and the genetic factors that contribute to the disease continue to be unraveled.