Incidence and Causes of Wilms Tumor
Incidence of Wilms Tumor
Wilms' tumor is the most common form of kidney cancer in children. About 500 new cases of Wilms' tumor are diagnosed every year in the United States, and this number has not changed in many years. Wilms' tumor makes up about 7% of all cancers in children. The incidence of this tumor peaks at about three years of age, and becomes less common as children get older. It is very uncommon after the age of six years. Wilms tumor is slightly more common in girls, and among African Americans.
Wilms' tumor usually affects only one kidney. This is referred to as “unilateral” because it occurs on only one side of the body. About 5% of children with Wilms' tumor have this cancer in both kidneys ("bilateral").
Other tumors of the kidney
Approximately 15% of kidney tumors are childhood are not Wilms' tumor. Other kidney tumors include:
- Clear cell sarcoma of the kidney
- Renal cell carcinoma
- Malignant rhabdoid tumor
- Congenital mesoblastic nephroma
- Other kidney sarcomas
It is important to correctly identify these tumors becasue they are treated differently from Wilms tumor.
Causes of Wilms Tumor
The causes of all Wilms' tumor are not known. However, some of these tumors appear to result from changes in one or more of several genes. In the majority of cases, the genetic changes occur only in the kidney cells and not in other cells of the body. However, in some cases, other parts of the body are also affected. Some patients with Wilms' tumor are born with certain congenital anomalies, including absence of the iris of the eye (aniridia) or abnormalities of the urinary tract. Although it is rare, Wilms' tumor sometimes runs in families, which further supports a genetic connection.